ken grant
January 12, 2005, 02:58 PM
It is amazing how such a little change can make such a big difference in the feel of recoil in a 1911. :what: :D
For the first time today, I shot both a Colt Combat Commander and a Norinco Compact at the same range session. The Norinco seemed to have much less recoil than the Colt and didn't rise as much on firing.
The only difference in the pistols were the firing pin stops. The Colt had the stock stop in it and the Norinco had a stop 1911 Tuner had put in(oversized) with a very little radius on the bottom.
I plan on fitting stops to all my 1911's with the small radius on the bottom. It really makes a difference in recoil feel. :D

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January 12, 2005, 03:42 PM
Ken! Shhhhhh! Don't be givin' away my secrets now... :uhoh:

Wait! Nix that. :scrutiny: John Browning figgered that radius out dang nigh a hundred years ago... :rolleyes:

I guess old John Moses really did know his bidness... :cool:

R.H. Lee
January 12, 2005, 03:59 PM
ken- would it be possible for you to post photos of each firing pin stop side by side?

Thanks. :)

Old Fuff
January 12, 2005, 04:03 PM
Why Tuner ...

How can you be so easily fooled ??? This is something that the New School folks don't use, and is therefore hopelessly obsolete ... :neener: :D

R.H. Lee
January 12, 2005, 04:10 PM
Fuff has a point. Unless it is properly endorsed by a real Pistolsmith (tm), it may be a questionable practice.

January 12, 2005, 05:21 PM
Ken...I fear that you have awakened a sleeping giant. You've probably just
sold about 2,000 EGW firing pin stops with one stroke of the keyboard.
George oughta give you a kickback...or at least a discount on a few of the things. :p

Riley...The standard stop has a 7/32nd inch radius. The Ken has...was/is .075-.080 inch, with .078 bein' print spec.

Fuff...I just never took any of the new-fangled stuff too seriously I reckon. I gave myself a headache makin' a handful of the old design stops...and then 20 years later along comes EGW with the dang things semi-finished and oversized to boot...for 10 bucks a copy! (They're about 20 now)

Now then...I'll leave it to ya'll to figger out WHY it has that effect. :neener:
Keenan and Fuff know why. Thinkin' caps on and....GO!

R.H. Lee
January 12, 2005, 05:24 PM
Well, you see, the lower end of the firing pin stop is the part that contacts and pushes back the hammer on recoil. When it's radiused, it makes for a smoother, more even rearward movement of the slide, because the hammer begins to move sooner.

January 12, 2005, 05:31 PM
Riley said:

> a smoother, more even rearward movement of the slide, because the hammer begins to move sooner.<

Nope! You're thinkin' about it backward.


The smaller radius actually causes the hammer to move more abruptly...once it starts. :scrutiny:

R.H. Lee
January 12, 2005, 05:35 PM
oh yeah.....

Well, ya can see I ain't no Pistolsmith. :p

January 12, 2005, 05:55 PM
Riley said:

Well, ya can see I ain't no Pistolsmith.

Hey! Me neither! :D

R.H. Lee
January 12, 2005, 06:07 PM
OK Tuner, since you're not going to 'splain it (at least right away), I'll give it another shot. Since the hammer begins to move later rather than sooner, the felt recoil is reduced because........??? the time the pistol is in recoil is shortened?

Why does this stuff make my head hurt?

Black Snowman
January 12, 2005, 06:15 PM
Does it have to do with the lock time being extended by additional force required by the slide to get moving with the leverage being closer to the fulcrum of the hammer?

The bullet and gas has progressed down the barrel longer before the slide starts moving imparting more energy to the heavier mass of the gun and frame. When the slide does start moving it has a lower velocity so when it reaches the full back position it hits the frame with less force. So, the recoil impulse is spread out with more initially and less at the end of the cycle reducing muzzle flip and felt recoil.

Or something like that.

That should be close right?

Edit: I might be cheating though because I researched this before buying my Delta Elite ;) Mostly here:

Old Fuff
January 12, 2005, 06:29 PM
Tuner ...

You still ain't got it ...

To be a "piss-to'l 'smith you have to be a PROFESSIONAL ... :neener:

The reason that firing pin stop works is because it's the way John Browning designed it. Unfortunately someone in the Army decided it should be changed. Things haven't been right since. :fire: :mad: :D

January 12, 2005, 06:31 PM
There's a lovely discussion by some very smart people on another board with interesting thoughts - including talking about how nice it would be to have pictures - anybody have references to controlled tests with observed distinctions?

Of course as some have said comparing recoil in a 1911 across different shooters can be a waste - Layne Simpson reported trying to do a controlled test of ports and compensators with friction on a Ransom Rest and not getting anyplace.

Black Snowman
January 12, 2005, 06:39 PM
Don't let them get your goat 'Tuner (I know you won't anyway). Professional doesn't mean you're any good. Just means you're paid for it. ;)

To steal a member's sig line I saw a while back: Professionals built and operated the Titanic. Amatures built and sailed the Arc. :neener:

January 12, 2005, 06:42 PM
The Black Snowman nailed it square on the hittin' place!

The smaller radius decreases the slide's mechanical advantage in cocking the hammer. The slide is delayed for a fraction of a nanosecond, and bleeds off
a good bit of the recoil impetus. The slide moves a little slower and with less force, and softens the blow to the frame...quite a bit, as Ken noted.

Also...Since the slide's delay gives the chamber pressure a tick longer to fall off, the extractor doesn't have to work as hard to break the casing's grip on the chamber walls during primary extraction...and in some instances will actually allow surprisingly reliable function with the extractor removed. Other things contribute to that little trick...but I've seen some pistols that wouldn't quite do it...until the firing pin stop radius was reduced...and it pushed'em over the edge.

The small radius utilizes more of the mainspring's resistance to hammer movement...and allows the use of lighter recoil springs with little or no reduction in frame protection. So there you have it...The original, Browning-designed shock buffer...and it doesn't shred or fall apart every thousand rounds. :p

R.H. Lee
January 12, 2005, 06:47 PM
Brilliant! I actually understood that explanation. Thanks, Tuner :)

January 12, 2005, 06:52 PM
So how can we purchase these parts?? Or do they have to be fitted?

January 12, 2005, 06:57 PM
Clark made a good point, and spot on. Give 5 people the same gun and ammo, and all will report different recoil impressions. A side-by-side test,
like Ken's experience can be revealing though. Even better is to change only the stops in the same gun. The difference is real, and depending on the
mainspring and recoil spring load, it can make quite a noticeable difference.

Looky at what you started Ken! A genuine discussion! Kudos lad...Kudos! :cool:

Snake Eyes
January 12, 2005, 06:57 PM
Amazing. This is exactly what Ted Yost is doing to my Delta Elite, to keep the slide from beating the frame to death.

Just amazing what a quality oriented 'smith can come up with to actually solve little issues like this.

I think Ted has headspacing gauges too!

January 12, 2005, 07:02 PM
ROFL Snake Eyes! Go to your room! :evil:

Shootcraps, you can get the parts from Brownells. I think they're about 18 bucks now, unless you qualify for the discount...then they're 15. There are two types...Original/series 70 design, and Series 80. the one with the -100
prefix is the Series 80, while the -058 is the original or Series 70. I may be confused though...I'll check to verify and report back. If I don't get back with it, the above numbers apply.

Yes. They require fitting. They come with a dead square bottom and you have to cut the radius. They're also over-width and require filing to fit the slide. I do'em with a light press-fit to keep the extractor honest. Fit to the slide without the extractor first and check firing pin operation...Then fit with the extractor in place.

Old Fuff
January 12, 2005, 07:03 PM

>> ... but I've seen some pistols that wouldn't quite do it...until the firing pin radius was reduced...and it pushed'em over the edge. <<

TYPO ALERT!! I think you mean "firing pin STOP radius was reduced."

Of course I am perfect in respect to typos ... and only my ego exceeds my good looks ... :uhoh: :evil: :D

Fuff...ya got me! yes...Firing pin STOP radius.

Cheers, ya old sharpie.

ken grant
January 12, 2005, 07:04 PM
Buy at Brownells and they have to be fitted.
Tuner told me how to do it. :D
It's also amazing the things Tuner can do at his kitchen table with a file,scrape and a stone. :what:

January 12, 2005, 07:08 PM
"bleeds off" ? - Can't fool Newton - where does it go?

I can see an energy delta going to heat in squeezing the rear of the slide/slide stop just a tad in a not quite perfectly elastic collision with the hammer - extra energy going to heat and vibration in the mainspring - but it sounds as though less energy is going into the recoil spring - what about conservation of momentum?

Sort of reminds me of the Blish lock - did that actually bleed off recoil to do just a little bit of unnecessary good?

January 12, 2005, 07:14 PM
Ah Clark! Picky picky picky! Shoulda gone into a little more detail. The
reduced mechanical leverage against the hammer and mainspring is the bleedin' mechanism. The mainspring absorbs the impetus at the beginning...the same way as a heavier than standard recoil spring slows the slide near the end of the recoil stroke...or maybe that ain't exactly the right way to explain it. :cool:

January 12, 2005, 07:16 PM
With the current fad of external extractors on 1911 Pattern pistols the firing pin stop does not have the keep the extractor from clocking does this make the fitting any easier?? I assume that an non series 80/schwartz safety pistolwould take an OS series 70 stop.

ken grant
January 12, 2005, 07:16 PM
Fast becoming my most favored pistol to shoot (after Tuner tunerized parts of it).
Put 15 mags thru it today(cast reloads), nary A bobble :D
Wonder if less radius on the stop will help the little baby 1911 copies? :confused:

January 12, 2005, 07:19 PM
I'm ordering them now. Thanks! I have a new Dremel tool with over 100 attachments so I can make anything fit anywhere. :D

January 12, 2005, 07:34 PM
>I have a new Dremel tool with over 100 attachments so I can make anything fit anywhere.<


ShootCraps...Put the Dremel down, back away from it, and nobody gets hurt.

HRT...Not sure which type stop the external extractor-ed pistols with the
Shwartz FP safeties use. I haven't been into one yet to see. They keep comin' up with this new-fangled stuff without tellin me, see... :D
Anybody familiar with Kimbers watchin'? We need answers!

January 12, 2005, 07:37 PM
Notice that some of the Bulls Eye greats would go the other way and radius the hammer to smooth the action.

ken grant
January 12, 2005, 07:40 PM
Where can you get gauges to measure Headspace of some of these so-called Custom Gunsmiths? :confused:
It would take a lowboy to deliver a gauge this size :evil:

January 12, 2005, 07:42 PM
Damn! They're out of stock. :cuss:

But my Dremel will be waiting for it. :what:

January 12, 2005, 07:45 PM
>Notice that some of the Bulls Eye greats would go the other way and radius the hammer to smooth the action.<

Ummmm...Okay! :cool:

Actually, I think that radiused hammer is to limit overcocking and to reduce
friction with the slide...but I don't have much truck with bullseye guns, so I really can't be sure on that point.

Jammer noticed pretty much the same thing as Ken did though...Said his old Springer is runnin' smoother with the small radius stop.

Old Fuff
January 12, 2005, 11:33 PM
On Bullseye guns ...

Sometimes the front of the hammer face was radiused to delay the hammer's backward movement. This in effect gave the slide a running start and was usually used in so-called softball guns combined with light 185 or 200 grain mid-range loads. It also worked well with .22 conversion units. John Browning would have just shook his head, but in some applications it worked very well.

January 12, 2005, 11:52 PM
You explained the softer recoil due to the radius of FP, very well and I appreciate it - thanks!

Is this called , or part of what is called Dwell Time?

January 12, 2005, 11:59 PM
ken- would it be possible for you to post photos of each firing pin stop side by side?

As I'm having some trouble picturing how it looks and how it works, I second that, please-or a drawing, or something. Please and thank you-the 1911 godz will pay you back Tuesday for this hamburger you give me today :)


Old Fuff
January 13, 2005, 12:21 AM
I'll try to find a picture, but for the time being look at the firing pin stop in your pistol (or just a firing pin stop) and think of one that is as flat on the bottom as it is on the top. Today's firing pin stops are rounded at the botom when you look at it from the side. What Tuner is talking about is more square and less rounded.

January 13, 2005, 01:08 AM
A good EGW picture will show up as #296-000-058
STI picture shows nice contrast as 791-112-045
both of these page 98 in the Brownell's catalog or on line.

January 13, 2005, 04:28 AM
Fuff said:

Sometimes the front of the hammer face was radiused to delay the hammer's backward movement.

Yo Fuff! Clark shot me a PM and described the mod. Once he mentioned Behlert, I knew what he meant. I had it in my mind that it was the angled face that Ken Hallock used to do. I recently did a slight modification on a hammer and a FP stop...gave it a larger radius...on a softball gun that I fixed up for Kelie. The 5-inch gun cycles smartly with 185 grain SWCs loaded to
600 fps Feels like a 9mm. Now, if I could just save some of the ammo for her.... :rolleyes: :D

Old Fuff
January 13, 2005, 09:44 AM
Actually it was Austin who first showed me the trick. If you are building a specialized bullseye match pistol using powderpuff loads this is the way too go. This is particularly so with heavy (ribbed) or long slide pistols. Service pistols and hardball guns are entirely different. What we have here is a "tools vs. toys" issue. Both methods are correct when used for a particular purpose.

When the slide recoils the firing pin stop presses against the hammer face and cams the hammer backwards. Depending on how much the stop is radiused on the bottom, and the shape of the hammer face, the resistance the hammer presents to being rotated will be relatively light (good for some kinds of match guns) or heavy (good for service pistols or other firing heavy ball loads). During the slide's cycle the hammer (which is under spring tension) works as a brake along with the recoil spring to slow the slide's velocity. Where the recoil spring is most effective at the end of the travel the hammer does its thing at the begining. This is important because within micro-seconds you want to keep the slide and barrel locked together until the bullet has exited and breech pressure dropped. After that the recoil spring's main job is to return the slide to battery. Too many people try to control recoil by installing extra-heavy recoil springs. This is often a mistake if the pistol is correctly set up the way Browning intended, and as Tuner has explained. The EGW firing pin stop comes with no radius on the bottom so the 'smith can shape it for whatever he has in mind. In the matter under discussion this is important because it is the only stop on the market that isn't over-radiused in the first place.

Old Fuff
January 13, 2005, 11:34 AM
O.K. ....

The attached is a picture of an EGW firing pin stop. On the left you see it as it comes from the manufacturer. On the right you see the small radius that Tuner has explained. I'll leave it to him if someone wants more details. Clearly this man knows what he's doing. I would observe that the modification may make it harder to pull the slide back by hand (which is why the Army made a change to the current configuration with a larger radius) but making the slide harder to move rearward is the whole idea.

Edited to add: The picture didn't come through - I'll try again.

January 13, 2005, 04:00 PM
Riley...The standard stop has a 7/32nd inch radius. The Ken has...was/is .075-.080 inch, with .078 bein' print spec.

You and I have talked about me doing this to one of my guns before but I haven't gotten around to it yet. I will try and order a FP stop but I had a question as to how to accurately measure that .078" radius.

Also, are you sure about the new standard being 7/32? That's a big jump from .078" to .21" it seems.


January 13, 2005, 04:28 PM
Hey Greg,

The way to accurately measure it is with a radius gauge...but a good set is pricey, and it's not imperative that it's precise. Use a 5/64ths inch drill rod to estimate it. The radius of the rod...half the just about right. Just hold the rod up to the bottom corner to see about what the radius should be and duplicate it as close as you can. It's important that the cut is kept even and straight across though. If it's
not, it'll cause a side load on the hammer pin. This is more important than
the radius being precisely .078 inch. Since I cut mine freehand, I doubt if any of'em is exactly on the mark.



EDITED TO CORRECT DRILL ROD SIZE! Use a 5/64ths rod to estimate the radius by aligning the edges of the rod with the corner. Sorry...hasty
instruction make for bad results.

January 13, 2005, 04:40 PM
Thanks for futher explanations and the pic folks!


January 13, 2005, 04:43 PM
IANAP! (I am not a pistolsmith). And Tuner has forgotten more about 1911's than I ever even hope to know. :)


I don't think that the differences here would be reliably perceptible by any normal human being. I think this is probably a false perception. Something I think that even the venerable Tuner might fall prey to from time to time.

The only way to know is to run double blind tests.

Can Tuner or some other advocate do this? I am sure you know how.

Lacking a double blind test, I call BS. It just "don't seem reasonable". Sorta like wine tastings -- with the blindfolds off, everyone is sure that the $200 bottle of wine if far superior to the $10 bottle. With the blindfolds on, no body can reliably spot which is which.

R.H. Lee
January 13, 2005, 04:48 PM
Thank you for the photo, Fuff. It looks like what Tuner recommends is juuusst a leeeetle more than breaking the edge of the firing pin stop. It looks quite a bit different than the fps on my Springer, which has a more pronounced rounded radius.

January 13, 2005, 04:57 PM
Sorry guys...I put in the wrong drill rod size in my response to Tarpley. See the edited text.

As an alternate method the EGW stop can be beveled lightly to just break the corner and stoned to blend it into a more rounded shape. I prefer the full radius, but either will work.

The egg asked:

The only way to know is to run double blind tests.

Can Tuner or some other advocate do this? I am sure you know how.

Sure. Just cut one with the radius and use a standard stop in the same pistol. Yes...I've done it. Yes...there is a difference in felt recoil and muzzle flip. Another test is to use a shock buff and see how much longer they last
with the small-radius stop. Again, the difference is the result of the mainspring absorbing a little of the slide's energy and delaying it for just a
fraction of a nanosecond before the slide gets moving. Thus it "bleeds off" a little of the recoil energy in the beginning of the cycle, rather than depending on the recoil spring alone to handle it. Simple physics. If the mechanical advantage used to compress the mainspring is reduced, the slide has to work harder to overcome the spring's resistance to compression, and that takes time. Time to let the chamber pressure drop...Time to get the slide moving at full speed...Time to cock the hammer against the mainspring. The delay is
very short, but things happen fast inside the chamber and barrel. Once the hammer is cocked, the influence of the stop is over...but its mission has been accomplished and the slide moves a little slower as a result. Lower slide speed means less shock when it hits the frame. Less shock means less felt recoil.



January 13, 2005, 05:04 PM
I thought that was a little too much radius at 5/32".
For what it's worth,the radius on my Officers ACP is 11/64"(the only one out of the safe to check),so 5/32" wouldn't be much improvment. :)

January 13, 2005, 05:07 PM
Dang - I love these threads! :)

January 13, 2005, 05:18 PM
gamachinist... :rolleyes: :D

I was thinkin' in half diameters there. Gotta slow down and stop tryin' to eat
while I do this! :p

January 13, 2005, 05:32 PM
Hey Tuner, what you are describing is not double blind -- maybe you did it, but just have not described it, here.

I just wish we were closer together, we could set up a test in short order to prove this thing one way or another. Basically, neither the shooter nor the person administering the test can be allowed to know which gun is which. Then, in a random manner, the shooter(s) fire the weapons and try to identify which is which. Enough rounds must be conducted to allow enough guesses to be made to determine if there is a statistically valid pattern (can you really tell which is which, no foolin'?) , or if it is just guessing (which would be my guess!).

And I would even be willing to wager a shilling or two on the outcome!!!!


January 13, 2005, 06:16 PM
I wouldn't think it would be that hard to check measurable recoil with a recording gauge attached to the trigger guard with a Ransom Rest.
But felt recoil is another matter,as it varies from person to person.
You would have to use the same gun and ammo,with the only difference being the firing pin stop to really be scientific about it though.
ga anamedpersonontheinternet machinist
(with apoligies to wild fillintheblank alaska))

Old Fuff
January 13, 2005, 06:51 PM
At one time the Old Fuff conducted some experiments with a Colt equipped with a .22 conversion kit. The main problem with these kits was that the slide was too heavy for the little rimfire cartridge to move. There was a marked difference if the firing pin stop was fully radiused across the bottom, and it and the hammer face were highly polished. The intention here was to reduce the effect of the hammer (and its spring) acting as a brake, which is the opposite effect that you'd want on a service pistol firing ball loads or hotter.

While some may find a difference in felt recoil, that isn't and wasn't what I was interested in. Better reliability and less battering of the frame and slide was, and still is.

As a side note: Browning's earlier pistols, and the blow-back .25, .32 and .380 pocket pistols all have a small radius engagement in the slide where it contacts the hammer face. This feature that Tuner has pointed out was a standard procedure with Browning, and not limited to the 1911 design.

ken grant
January 13, 2005, 06:59 PM
The feel of the recoil is all I am interested in. If it feels less,it must be less.
I didn't intend to test anything when I went to the range. I thought the Norinco recoiled less from earlier firings but had never shot the two of them together.
At this time ,I did shoot both of them together and proved to myself that the firing pin stop did make a difference.
I suggest that if you have any doubts,that you make your own tests.

I am happy with my results and do intend to put the same stops in all my 1911's :neener:

January 13, 2005, 08:55 PM
Just curious...does anyone know why the Army dictated the radius change to the original Browning firing pin stop design? Seems to me that the larger radius might improve reliability under battlefield conditions...might also increase service life by reducing forces on the hammer/pin...all at the expense of sight recovery and general shootability. I guess if one had to choose between reliability and about anything else under the most adverse conditions imaginable then reliability would win! For me, any improvement in shootability would be appreciated more, however, as a fairly heavy lead user I'd still be concerned about service life...if that's an issue here at all.


January 13, 2005, 09:21 PM
bullseyeboy asked:

>Just curious...does anyone know why the Army dictated the radius change to the original Browning firing pin stop design?<

It was done to make the gun easier to hand-cycle with the hammer down.
The biggest majority of the soldiers who were authorized to carry the pistol were restricted to Condition 3 carry...Magazine loaded, hammer down on an empty chamber...which required that the slide be cycled to ready the gun
for action. Some of the lads complained that it hard to do in a hurry, and
the Ordnance Department went back to the drawing board.

Rumor has it that several of the custom smiths who build the gun in 10mm
have found that the original radius on the stop allows the gun to be used with
18-20 pound recoil springs rather than the more common 22-24 pounders...
with no loss in frame protection. Seems like I also heard that the final recoil spring rate was determined by the mainspring rate. I may not correct on this point, but it does make sense.

There's also a "clew" there for the folks who lighten the mainspring load in order to lighten the trigger action...without compensating for the reduced
braking effect of the lighter mainspring. :uhoh:

Think about it... :scrutiny:

Old Fuff
January 13, 2005, 10:51 PM
I agree with Tuner again. (I would have had the answer, but his keyboard is faster ... :scrutiny: )

The Army had experimented with Browning designed/Colt .38 automatics, and then a whole bunch of .45 prototypes. All were carried in full-flap holsters, and quick draws weren't on the program. Before a change was made on the firing pin stop some would draw the pistol (slowly), cock the hammer, and then cycle the slide. Of course someone complained, and the change followed.

It has been wisely said that when you change or modify something in this pistol at least two or three other parts and/or they're function will be affected. Unlike most handguns it was not designed - it was developed over a period of five years (twice that if you count the earlier .38 pistols) and as defects or problems were discovered they were corrected in the next prototypes. After the design was finalized in 1910 and adopted in 1911 few additional changes were made during the whole time it was used by the military services, and today's commercial guns are little different then the first guns except for cosmetics and materials.

January 13, 2005, 11:45 PM
It was done to make the gun easier to hand-cycle with the hammer down.

Which is also the best way to test and prove the theorum.

Try it yourself and you will be able to FEEL the difference in the force needed to retract the slide with the hammer down.

January 14, 2005, 07:14 AM
BluesBear said:

Try it yourself and you will be able to FEEL the difference in the force needed to retract the slide with the hammer down.

Exactly so...and you'll notice that the extra resistance is at the very beginning of the cycle.

The mechanics are very simple. The slide isn't driven through its full travel...only during the first 1/10th inch of movement. There is a set level of energy produced when the gun fires...and that energy is established in the time during the first .100 or so inch of slide travel. Once established, only momentum completes the cycle.

The small-radiused stop...due to a lower point of contact and reduced leverage (mechanical advantage) against the hammer...causes more of that limited amount of energy to be used in moving the hammer, and it does most of that during the onset of hammer rotation...or in the first 1/10th inch of travel.

Since the hammer also has mass, its inertial resistance to movement is also
figured in...and like any other object...once motion is established, momentum
helps to keep it moving...BUT...the slide still has to work to start the process.
To simplify it...the slide has to work to accelerate it from a dead standstill, and some of the energy is dissipated in getting the hammer to move.
The more energy it takes to get the process started, the less momentum available to keep the slide moving...hence the reduced impact and felt recoil when the slide hits the stop surface in the frame.

Other factors must also be considered. Mainspring load...Hammer mass/weight...Even friction...but if all else is equal, the slide's speed and momentum will be reduced after the hammer is cocked.

January 14, 2005, 09:19 AM
'Tuner, I smell a Saturday project... Say around noon? :D

January 14, 2005, 09:57 AM
Well, I bow out.

It seems I am heavily outnumbered by the "my subjective perception is reality" crowd.

Can't really argue with that. Nor do I want to.

Ya'll have fun now!!

January 14, 2005, 10:15 AM
I would say the reduced radius FP stop has the effect of slowing the slide down a "tad" due to the lack of mechanical advantage against the hammer and mainspring. This retards the shooter's impression of the whack that happens in a normal fitted out pistole when the slide hits the end of its travel. The whack is still there, it's just not as ABRUPT and it's partially taken up by the mainspring.

How'd I do, Tooner? :p

Old Fuff
January 14, 2005, 11:04 AM
Sometimes the forest gets missed because of too many trees …

The original Browning-designed firing pin stop was intended to reduce battering between the slide and frame to insure greater longevity in the operational life of the pistol, and to better control the timing of the slide’s cycle to increase reliability. Tuner’s experiments and observations contained in an earlier post showed this is the case. (If plastic recoil spring buffers last substantially longer something is going on).

A side effect of using the small-radius firing pin stop is less felt recoil. This is subjective on the part of different individuals, but Ken is obviously sold. Others may or may not be, but it would seem likely that if the slide comes to a “softer stop” at the rear end of its travel the felt shock would be less. If one is using a pistol with a lighter slide (read that “sub-compact”) the effect might be more noticeable. In any case the mechanical principals are one thing, and subjective issues concerning felt recoil are another.

This thread has been, and continues to be especially valuable because it brings to light something that few 1911-pattern pistol owners know about, and for that we can thank both Ken and Tuner. One may, or may not decide to try a different firing pin stop, but for around $20.00 it offers an interesting option, and it is far more likely to be helpful then many other more expensive gadgets and gimmicks being sold as aftermarket accessories.

Black Snowman
January 14, 2005, 11:54 AM
As part of my "Master Plan" (tm) for my Delta Elite my latest update has been going from the stock FP stop to the EGW peice, fitted, with NO radius. This was after going to a convetional 20 lbs recoil spring, a standard steel guide rod, and a 25# hammer spring to try to get the recoil impulse to be more comfortable.

I'm also intentionally leaving the heavy stock hammer in place in the hopes that it's extra mass will assist in extending the unlocking time as well. I can't find anyone who carries an extra heavy version. People seem to be obssessed with their lock times and cycle time when it comes to aftermarket hammers :)

Changing the slide stop made more of a differance to me than raising the hammer spring pressure 2 lbs and I can shoot the gun accuractly with noticably shorter split times.

However, I'm still getting an occasional FTExtract. Particularly with my full power 135 gr loads when the gun is dirty. Perhaps I need to look at the chamber condition and I know I still need to check the extractor tension. Every 25-50 rounds one will just stay in the chamber. But I'm not going to hijack this thread with my problems, I already know where to look to narrow them down :)

January 14, 2005, 12:45 PM
Black Snowman...Don't leave the corner sharp. If you want minimum leverage, just lightly break it on a narrow bevel. Your hammer will thank you.

Close BigG...but it's not a perception. It really does soften the blow.

Egg! We're not tryin' to shout ya down. We're tryin to eddy-cate ya. :cool:
While I completely agree that felt recoil is subjective and varies from one person to another, there is a provable, mechanical reason that the recoil is reduced. Why is it reality and not a subjective perception? Because a
mechanical change has been made that reduces the available force necessary to propel the slide to full travel. More force required to cock the hammer means less momentum remaining AFTER the hammer has been cocked.
Less momentum means that the slide is moving slower. Less slide speed means less impact energy when it hits the frame. Simple physics.

Let's try an imaginary experiment and see if it makes more sense.

Fact: The reduced mechanical advantage in cocking the hammer requires
more of the slide's momentum to perform that function. Simple machine...The closer to the fulcrum (the hammer pin) that you put the force (the recoil momentum transmitted via the slide) to the load (the hammer's mass and the mainspring's resistance to compression) the less total force is available to
complete the cycle once the extra resistance has been overcome.

You, plus a theoretical friend and a basketball decide to put it to the test.

Your friend holds the ball between his hands in front of him at arm's length with just enough force to keep the ball from falling.

You punch the ball with a hard right cross of say...200 pounds feet of energy...and knock it into his chest. Assuming that the ball's mass and inertial resistance and the friction imposed by his hands absorbed 10% of
the energy...the ball strikes his chest with some 180 pounds feet of force.

In part two, your friend holds the ball again, but this time he presses inward
on the sides of the ball with all the strength that he has. You punch the ball with a theoretically identical right cross...200 foot pounds again. The force
that your friend is exerting on the ball requires more of the available energy to dislodge from his hands and send into his chest, but the force of your punch is the same.

Everything remains the same except the frictional resistance to the ball's acceleration imposed by the force that he exerts on the ball. Agreed?

Your punch is the recoil impetus. The ball is the slide. His chest is the frame's impact surface. His hand pressure is the difference between the two FP stops, and is thus the only thing that changes the ball's resistance to acceleration.

In which experiment is your friend's chest going to take a harder impact from the ball? Do you think that it's only his perception of less impact when he tightens his grip on the ball...or is it reality? After the punch...Will the ball
move toward his chest at the same speed in each case..or will it be slower
when he grips the ball tighter?

Do you reasonably expect that the ball's impact against his chest would be the same in each scenario...or do you expect that it would be reduced with a tighter grip on the ball?

Standin' by...

January 14, 2005, 01:25 PM
Tuner --

You have missed my point completely (I think!). My point is that it will be impossible for a human being to be able to perceive the difference in forces you are discussing during the act of firing a 1911 .45 acp pistol. Any one that claims to be able to do so is, in my opinion, deluding themselves. I have suggested a method to prove this one way or another.

However, OF COURSE changes in the design or specifications of things like the firing pin stop, and indeed any of the elements of the machine, will influence the operation of said machine in some way. I am not disputing that at all -- it would be silly to do so. I am focusing in on the fact that the changes you are discussing in this particular thread can't be detected by a human being -- they are too small for the human sensorium to sort out!!!!!!!

And with that, I really am out of here. The weekend is almost upon us, and I have some shootin' to do.

Oh, and by the way Tuner, it has been proven conclusively by better men than you, that I am uneducable. :neener:

January 14, 2005, 01:38 PM
the Egg insists that:

The changes you are discussing in this particular thread can't be detected by a human being -- they are too small for the human sensorium to sort

Nope...they are detectable, and you don't have to go to the trouble if fitting a firing pin stop to feel it. Just get one 21-pound and one 25-pound mainspring and swap'em back and forth. Use a fresh shock buffer with each mainspring to begin the test and see which one shreds first.

The difference between the two stops is about the same as the difference between a 14 and an 18 pound recoil spring...or the two above mentioned mainsprings. It really is that much. I'll conduct the test...but it'll hafta wait for a better time. Got way too many pinto beans on my plate right now.

And...the only man that I ever met that couldn't be educated was my brother-in-law. :neener:

ken grant
January 14, 2005, 02:01 PM
I don't guess that I am a human being. The first time I fired the Norinco after Tuner installed the stop,I noticed the difference in the recoil feel. I fired it several times afterwards and always felt the same.
This week when I fired it along with my Colt of the same size,I could really tell the difference in feel.
Same ammo,same size pistol,same springs and same day. I didn't mention the fact that a friend was with me and fired both as well and he had the same feel as I did.(maybe he is not human as well)
No matter who is right or wrong as long as I like the feeling that I get,I am happy :neener:

January 14, 2005, 02:03 PM
Egg, dunno about a double blind test, but I do know for certain that a small radius firing pin stop was part of the solution to correct some timing/reliability issues in a Colt Officers Model.

That isnt a subjective opinion. Before the EGW firing pin stop was installed, the pistola wasn't reliable. After installation of the EGW part, it is reliable.


Black Snowman
January 14, 2005, 03:43 PM
I'll take your advice 'Tuner. I'm refinishing the gun tomarrow so I've got it all apart anyway. Only excuse I have is I can't seem to find what I did with my stones . . . [shuffles feet through piles of junk on the floor while looking about]

Old Fuff
January 14, 2005, 05:32 PM
Ya don't neeed a stone dummy ...

Just go find a loose brick ... :neener: :D :D

January 14, 2005, 06:17 PM
Loose brick...aka Field Expedient Abrasive Tool...but if you're not too far from a hardware store, a sheet of 320-grit wet or dry paper on a piece of glass will do. Hold the corner on a 45 degree angle and pull it sideways across the paper evenly to break the corner straight across.

Saltydog mah fren! Good to hear that little beastie is still doin' ya right.
The FP stop was just a small part of the timing puzzle. Believe it or not,
I've got another OM that's more stubborn than yours was! I finally squashed all the bugs on the 3rd try. :rolleyes: It's runnin' and ready to go home now. :cool:

Ken buddy! You and your range pal ain't the only ones to notice that little side benefit. I did one up for a guy a while back without tellin' him about it,
since I had to fit an oversized stop to keep the extractor from clockin', I figured..."Why not"? When he called me to report on the test-fire session, he remarked about how his new lot of ammo must be "weak", since the gun wasn't as bouncy as it was with the old lot. :D Sellier & Bellot hardball, I think it was.

ken grant
January 14, 2005, 07:20 PM
Maybe if we sent a print-out of this thread to EGW, they would treat us right on prices for F.P. stops :D

January 14, 2005, 07:54 PM
Ken said:

Maybe if we sent a print-out of this thread to EGW, they would treat us right on prices for F.P. stops.

Yeah! Qualify for a 20% discount if ya tell'em...Toooona sentcha. :cool:

Money says that George is well aware that we're talkin' about his stops even as we speak. :p

January 14, 2005, 09:50 PM
Well, I am early to the party, but late to this thread. Not sure where I first picked up on the advantages of the EGW fps, but I am sure it was reading about different people's experiences with their Delta Elite's. Anyway, I ordered one, and had the good sense to follow Tuner's advice about breaking the edge. This was a used gun, but I estimate the mainspring to be about 25 pounds, definitely longer and stronger than stock. The previous owner's recoil spring was probably 28 pounds! Way too much!

Sidebar; Tuner, have you ever seen a change in recoil spring cause a change in point of impact? Like 4" at 25 yards?

To make a long story short, minor modifications will probably cause less problems than major modifications. The combination of a slightly heavier mainspring, a slightly heavier recoil spring, and a slightly less radiused firing pin stop all add up to a 10mm which shoots much better. If Colt had done this the first time around, I bet that the Delta Elite would still be in production. Of course, that tungsten recoil spring plug is just icing on the cake.

Yes, it is hard to rack the slide with the hammer down. No problem, simply cock the hammer first. ;)

January 18, 2005, 02:41 PM
:fire: Ok you guys, I tried to order two EGW firing pin stops from Brownells this weekend and they're out! Must be you folks bought them all, thanks to this thread and Tuner. :what: Now I have to wait. :cuss:

January 18, 2005, 02:46 PM

Unless they've sold out of'em in the last two weeks, the Series 80 type stops will work in either design. PN 296-100-001. Price is the same.

January 18, 2005, 03:01 PM
Call Practical Shooting Supplies at (800) 554-3230. They have them in stock. Mine was $14.00 shipped.


February 9, 2005, 02:52 PM
I wanted to bump this for those interested.

I got my FPS in a while back and had time today to fit it. Took about an hour to file down the sides (same amount off of each side based on the previous stop). I made it a tad tighter than the old one. I rounded the radius using a 5/32" drill bit as a guide like Tuner said then polished off with 320 and 600 sandpaper making sure that the shoulder stayed even all the way across. Reblued using cold blue and installed in gun. Function tested fine and wasn't nearly as difficult to rack the slide as I had been led to believe. Took it to the range and test fired with no issues. I cannot really tell if the recoil is reduced or not. Won't really know till I get on a clock with it.

Thanks Tuner for your help.


February 9, 2005, 04:55 PM
Howdy Greg,

You may not have noticed much difference if you're using a lighter than standard mainspring. That's part of the whole enchilada, and it doesn't really start showing up until the mainspring load gets up above 21 pounds.

February 9, 2005, 05:22 PM

I am using a standard mainspring...whatever that # might be. I toyed with the idea of lightening it but I didn't based on your recommendation a while back. On a side note though, I have really got this gun tweaked out now and I LOVE shooting it now.


February 9, 2005, 11:07 PM
How much does the firing pin stop modification increase recycle time? Is the increase in time offset by greater control? I know this is picky, just wonderin'.

February 10, 2005, 06:22 AM
Well, I can detect no perceivable delay over what I had. I CAN tell you that during double-tap drills yesterday, it seemed like I was back on target a tad faster than before. 'course that could be because that was what I was expecting. Like I said, I really won't know if this is a definite improvement until I get on the clock at the next match.


February 10, 2005, 07:30 AM

You won't have any perception of a delay. The difference is what you noticed. Since a little more of the slide's momentum is absorbed at the beginning by the mainspring, it doesn't hit the frame as hard...and the muzzle flip is reduced when it does hit. The stronger the mainspring, the more difference you'll notice. Standard is 23 pounds. It's a different "feel" than just using a stiffer recoil spring to soften the impact, since the recoil psring tends to push against you as the slide moves. The small radius/stiff mainspring soaks it up right at the beginning and over just a tiny amount of slide travel. Once the hammer is cocked, its effect is over...except that the slide's speed and momentum is reduced before the recoil spring really has an effect.

Interesting dynamics when really study the whole effect...and more noticeable when you swap FP stops and try'em back-to-back.

February 10, 2005, 04:02 PM
i looked at my sa milspec and it already had that done to the firing pin stop i guess i dont have to do it myself

February 10, 2005, 04:47 PM
Howdy stealthmode,

Your Springer's stop has the 7/32nd inch radius at the bottom. The one we're using is the EGW square-bottomed stop with a smaller .078-inch (nominal) radius that has to be hand-cut, and was the standard radius in the original design before the Army asked for the one like yours. It was requested in order to make the pistol easier to hand-cycle with the hammer down.

February 10, 2005, 05:21 PM
I'll post a pic tomorrow when I can upload from the camera so you can see what we're talking about.


February 11, 2005, 07:27 AM
Okay, here is a somewhat blurry pic of what the before and after looks like. The FPS in the foreground is the one that came on my Kimber (current design) and the one in the background is the original JMB design.


February 11, 2005, 08:15 AM
Good pictures Tarpley. Thanks! It may be the lighting, but the finished
radius looks a bit larger than .078 inch...and is larger than I use. If that's
a correct assessment, that may be why you don't feel a lot of difference
in the recoil. Hard to tell from here, though... :scrutiny:

February 11, 2005, 08:44 AM
What is the correct size drill rod to model radius after??? 5/64 or5/32.

February 11, 2005, 09:11 AM
I used a 5/32" drill bit to gauge mine. That was based on a PM from you 'Tuner. Is that the right size? And, yes, it is the same size as that _5/32"_ bit.

edit to add: I think I have discovered the error...5/32" is .16" and 5/64" is .08". I think I was supposed to use a 5/64" bit.

edit again: 'Tuner, I see you corrected the spec for the drill bit. Cool, I was going to suggest that you do. I had originally questioned how we got to .078" using a 5/32" anyway. Now I know what happened. I will leave it as is...seems to be a good compromise.

5/64 = .078


February 11, 2005, 09:35 AM
It's the 5/64ths bit...My apologies Greg. I had my head screwed on backward that day...and made the same mistake here on the thread. I was thinkin' in half diameters and didn't catch it before gamachinist did.

Your radius will slow things down quite a bit...just not as much as the .078 radius will. I'm gonna call Brownells today and order a few things. I'll have'em toss in a new EGW stop and send it...or...if they're still out of stock on the pre-80 Series type, you can order one from EGW and I'll pay for it in exchange for the stop you have pictured. I can always find a use for it.
let me know how you want to do it.

Again...My apologies to all for my brainfart on this project.

Standin' by...

February 11, 2005, 09:54 AM
No problem...I'll keep the one I have for now. It seems to shoot really well now. I may tinker with another one later on.


February 11, 2005, 10:05 AM
After reading this thread yesterday I went home planning on working on the FPS on both of my 1911s, but when I looked at them they both have the FPS like the blurry one in TarpleyG's picture. One is a Kimber TLE II and the other is a Springfield Mil Spec.

So the question is am I already getting the lower felt recoil or should I replace the FPS with one modified like 1911Tuner suggests?

February 11, 2005, 10:13 AM
Greg...I'm already on it. Brownells still outta stock. :fire: I'll call EGW and order direct. I'll be ordering 5, and will hold one back for you. I'll go ahead and put the radius on all of'em, so all you'll need to do is fit it to the slide...
Let me know when you're ready. My mistake...My responsibility.

Tallgrass...You'll get the reduction over the now standard stop...but it won't
provide quite as much difference as the .078 radius. Looks like somebody caught on to the return to original mindset...thought that the .078 radius
looked a bit too brutal...and split the difference. Interesting.

FWIW...One of the top guns in the custom industry tinkered around with that radius in a 10mm pistol and found that he could get the same frame protection
with the EGW stop and an 18 pound recoil spring as with the 7/32nd radius and a 22-pound recoil spring...with reduced muzzle flip to boot. IIRC, it
was Ned Christiansen...but I may be mistaken on that, so don't hold me to it.

Standin' by...

February 11, 2005, 10:15 AM
You have to but a new firing pin stop. A company called EGW makes one that is both oversized and that has a square corner where that radius is. You have to first fit it into the channel like a normal FPS then you have to radius the bottom edge to a 5/64" (.078") corner.

Go back and reread the thread and you'll understand better what is going on.


February 11, 2005, 10:17 AM

Shoot me a PM when they get in and I'll let you know where to send it. Unless, of course, you still have my address from before.


February 11, 2005, 07:33 PM
I have made no scientific measurements. My Delta Elite with an 18 pound recoil spring, and an unknown, but definitely 23+ mainspring, (probably 25, it came with the gun), plus the small radius firing pin stop, flings ejected brass about 2 feet further than a stock Gov't model firing factory hardball.

This is with a heavy load of Power Pistol, and 180 grain bullets.

If Colt had used this setup, I think that they would still be manufacturing Delta Elites. :)

No voo-doo, no black magic. Just simple physics in action.

Before the addition of the small radius fring pin stop, the same loads in that gun would send brass halfway into the next county, even with a 20 pound spring.

I am sold on the concept. I am thinking about using the reverse side of that concept in a 9mm Gov't model. Works both ways.

February 12, 2005, 03:25 AM
great pic now i see a difference. i will now have to try that mod

thanks :)

April 25, 2005, 08:20 AM
Any available in stainless? OTOH, I've had a blue extractor in my electroless nickel Colt for years until I found one in stainless and it never bothered me. I'm not running out and replacing any on a working gun, but I'll also replace the slide stop with one of these EGW ones next time an extractor breaks as the quality of extractors seems suspect these days.

Good thread. Someone should send this to Kel-Tec, I bet this is the basic problem with the P3AT extraction issues -- too rounded at the bottom of the slide to make up for the heavy recoil springs on the little gun.


George Smith
May 13, 2005, 11:21 PM
Pretty Kool :D
100 posts about a firing pin stop.
The part is machined from Oversize A2 stock, No mim need apply!
45 to 49 rc. We have sold about 12,000 so not so much a secret ;)
They should be selling for 15.00 retail. But if you act now, and check out our new shopping cart :) and mention in the note field that you saw offer #323 on the LTW forum we will sell you a stop for 13.00 plus shipping. and if you act now well throw in a shock buff :neener:

As to verification that it works.
First case study from Larry Stuerwald that was the gunsmith for Para for several years. He was having problems with P-10's leaving rounds in the chamber. We put a square corner stop in and it worked fine, took it back out and it started leaving cases in again.

Gary Heindman from Ace custom 45 uses it with his 45 super, he said because of the stop he was able to drop 4# in his recoil spring.

Very recently a customer was having problems with a very short Kimber with the same results, std stop and it would leave rounds in the chamber (external extractor gun) with the stop it slowed things enough that the gun funtioned fine.

Funny that you guys mentioned Austin, it just so happens I worked there for 4 years in the late 80's, and yes if raising the contact point on the hammer allows a light load gun to funtion it stands to reason lowering the contact on the hammer would do the opposite.

Thanks for all the positive feedback.


May 13, 2005, 11:25 PM
Welcome George!! :) :)

May 14, 2005, 04:18 AM
Welcome Aboard™ George !

May 14, 2005, 11:39 AM
Ladies and laddies...I give you Mr. Evolution Gun Works himself. :cool:

Howdy George! Welcome aboard.

I ordered 5 of those stops from you a few weeks ago, when Brownells kept tellin' me that they were out of stock. I don't know if it was you that I talked to or not, since I didn't ask and the guy I talked to didn't give a name...but he told me that anything that Brownells carried from EGW, I could order direct. I'll probably order a few more next week, since I made the mistake of doin' a few for the guys down at the range...and suddenly I've been swamped with requests for more. :eek:

The general reaction...besides the obvious...was: "What a great idea! Why didn't somebody think of that before??!!" When I told'em that somebody had
thought of it over 90 years ago, they were flabbergasted and mystified. To date, I've installed over 30 for for the PHA club members alone...with requests for 7 more as soon as I get settled in the new house.

As a side note...I've got an early 40s production High Power on loan here...
complete with internal extractor guessed it...a small radiused firing pin stop. 'Magine dat! :p

May 14, 2005, 01:06 PM
This is an prime example of how this site has so much useful information that is shared amongst its members.

I have a question for everyone.
What if the FP stop is not beveled at all? Would the slide be too difficult to retract?
Would this cause some type of malfunction or does it need to have, at the minimum, the 5/64th bevel?

Regards, Mercury.

BTW, Brownells has them in stock again.

May 14, 2005, 01:28 PM
Don't leave the corner sharp. If you want minimum leverage, just lightly break it on a narrow bevel. Your hammer will thank you.

Nothing else is quite like pounding on a sharp edge for stress cracks.

May 14, 2005, 05:52 PM
That sounds like good advice.

May 14, 2005, 05:55 PM
Howdy George and welcome! I just ordered 4 of those stops. Can't wait to try 'em out. :D

May 14, 2005, 08:45 PM
But did we ever figure out if the Kimber wants a Series 70 or 80 FP stop plate?

May 14, 2005, 11:52 PM
I'm glad this thread resurfaced. Today I was looking at a couple 1918's (or were they 1917? :D ) that have not yet been sucked into the void of no return in Tuner's basement. :evil: The "original" 1918 USGI has a small radius firing pin stop. The 1918 USGI Augusta Arsenel redo has the "modern" larger rediused stop.

I've shot both types of stop in modern 1911's. The recoil seems less with the smaller radius stop and it is quicker to return to target. It works for me. Thanks Tuner.

And thanks George! Your product is a welcome improvement. Welcome to our little pastime!

May 17, 2005, 10:59 AM
I'm new to this group. I've been lurking for a while and would like to add a suggestion. The pistol is different, but the concept is similar.
I have an officers ACP .45 that when the hammer was down had a small amount of play in the hammer. The hammer was not under tension. This gave the slide a running start before beginning to compress the main spring. Recoil was brisk. I installed a longer hammer strut from Cylinder & Slide Shop (via Brownell's) which placed the hammer in tension all the time. It made a slight improvement in felt recoil. I expect the same thing would help a 10mm. Even if there is no detectable looseness in the hammer, the increased tension would probably further delay unlocking.
Apologize for the user name. All the good ones were taken. Just ran a finger across the keyboard.

Old Fuff
May 17, 2005, 11:08 AM
You have a point. We usually start with the perception that the pistol has been correctly put together in the first place, at least until informed otherwise. Today too many firearms leave the factory without adequate inspection, and this is something we shouldn?t forget.

May 17, 2005, 11:11 AM
Howdy dhttuu, and welcome aboard! Bout time that ya came outta the shadows. :cool:

I run into the same deal once in a while. It's usually a spec issue or tolerances stacking up in the wrong direction. My fix involves facing a few thou off the top of the mainspring cap to let it sit a little higher in the housing. A quick-fix is just to remove the cap retaining pin and let the cap
ride fully up against the end of the strut.

May 17, 2005, 04:56 PM
I was curious about this myself from the start of this thread... Never thought that it would go this long and still not have an answer.

Good news. I just called EGW and talked with Jeff. Great guy and very knowledgeable. According to Jeff, Kimber owners can safely order a Series 80 stop for the Kimber series II in .45. If you have a series I or pre-series designation than a series 70 stop should be used.

I should also note that Jeff did say that a series 80 stop should work in most all 1911's out there. (I think early on Tuner said this as well)

Hope this helps!


May 17, 2005, 05:21 PM
It helps if it is correct.........but I have my doubts. A Series I Kimber and a Series II Kimber, unlike a Series 70 and 80 Colt have no difference at all at the extractor or FP stop plate. You can use either a Series 70 or 80 extractor in either a pre-Series II or a Series II Kimber. So, why would a Series II take something different than a pre-Series II? I'm of the opinion that either will work in either model.

May 17, 2005, 05:36 PM
He compared the Series 70 Colt to a Series I Kimber and a Series 80 to a Series II Kimber. He did also mention that the Series 80 would work in most all guns out there.

If there is no difference in the slides of either model, I dont know why either. Just figured that I would make the call and ask so that I could get some on order as well. Just posted what I was told. I dont have a Series I to take apart and measure. As has been noted before, they are really nice people over there - If you dont mind to make the call and clarify. Just be sure to post what you learn.


edited to add...
Quote from Kruzr here:

Kimbers (all of 'em that have them) take Series 70 type internal extractors. If there is a difference between a Series 70 and 80 FP stop (?), then you want a Series 70 for the Kimber.

The reason you need a Series 70 type grip safety for a Series II Kimber is the thickness of the arm. A Series 80 type has a thinner arm that won't engage the push rod for the FP block. The Swartz safety is not like the Series 80.
end quote

And that kinda nullifies your last post about there be no difference at the extractor or the FP stop from your own post. If I knew from personal experience I would have posted on that. I will take the info from EGW and run with it.


May 17, 2005, 10:31 PM
Did I miss something?

I see no contradictions in Krusr's posts.

In Colt guns there is a difference between a Series-80 and pre Series-80 firing pins. You can use a Series-80 firing pin in a pre Series-80 gun but not vice-versa.

As has been stated before the Kimber and Colt safties work differently.

May 17, 2005, 10:58 PM
He compared the Series 70 Colt to a Series I Kimber and a Series 80 to a Series II Kimber.
That explains his misunderstanding.

And that kinda nullifies your last post about there be no difference at the extractor or the FP stop from your own post. If I knew from personal experience I would have posted on that. I will take the info from EGW and run with it.

Where did it nullify anything? Was there something I did to offend you? I can't seem to find it. :scrutiny:
Run with whatever you want, apparently either will work (and take it easy on the coffee.)

May 17, 2005, 10:59 PM
I have a question about fitting the stop. It is oversized, but how? Is it thicker, so that all you have to do is sand down the back of it to fit it???

May 18, 2005, 03:16 AM
Many stops are slightly thicker and need to be slightly thinned.

But there's often more than that.

Most stops also need to be fitted to clear the ejector. For example Commander and .38 Super/9mm models have a differently sized ejector than the one used in the standard .45 Government model.

May 18, 2005, 06:44 AM
Thanks BluesBear. I'll compare it carefully to the original before I modify it.

George Smith
May 18, 2005, 01:47 PM
The Series 80 firing pin stop is cut for the series 80 lever on the right side and on the left for a Commander ejector.
This will fit any gun we know of. Govt commander officers, 9 38s 40 10 and 45.

The series 70 fp stop has no cut out on the right for the ser 80 (hence the ser 70 discription :rolleyes: ) On the Left side it is cut for a 5" 45 ejector.
the GI ejector.

As soon as you leave the 5" gun the ejector changes in almost all gun.
(SIG's smaller guns will probably use the 45 full size ejector)
So if you have a ser 70 commander in 45 the ejector will hit the fp stop.
same for any just about every short gun, commander or officers model.

IF you file out the path for the ejector you will most likely leave a square inside corner and as a commander it will be closer to the firing pin hole and crack through faster than you will like. The stops are both made with a corner radiused endmill to leave a .020 radius in the inside square corner on either side. If one fails we will replace it free, provided you did not file the radius out.

Kimber's series 2 safety is different from the Colt/Para ser 80 cut out.
if you have a 5" kimber you can use a ser 70 45 stop.

We made the stop to the widest slide cut out I have ever measured.
.482 you will almost always have to fit it side to side. if you do it by hand take a little at a time and check yourself with a caliper, hold it up to the light and see that you are strait and even, do one side and finish than the other, equil amounts.

they are .100 +/.0005 -.001 and you will have to remove stock from the stop or open the cut out in the extractor for it to fit some times.

This gage is what we use to check the slide size, you can than install the extractor and see how wide you want to be.

Sorry for any confusion we may have caused

May 18, 2005, 03:09 PM
George said:

...Do it by hand take a little at a time and check yourself with a caliper, hold it up to the light and see that you are strait and even, do one side and finish than the other, equal amounts...

This is easier to do by laying the file down and pulling the side of the stop lengthwise on the file, instead of clamping the stop and trying to control the file. It provides more control if you can arrange to have the file roughly at eye level, and draw the stop toward you.

Also...Once in a while, you'll find a slide that the stop is a little too thick to
fit into. Rare, but it does happen. Thin the stop from the forward side...(As oriented in the gun)...and cut by drawing the stop on the file. Remember to break the sharp edge around the hole lightly with a countersink or a tapered stone to prevent a stress riser/crack from forming, and to give the butt-end of the firing pin a smoother path.

George...I'll probably call tomorrow. The last 5 that I ordered have been spoken for, and I need a few more. :cool:

May 19, 2005, 12:46 AM
:) Hi Tuner,
Is "The Function of a 1911 - Part II" available yet? I don't know where I got Part I, so I cannot refer. I'd sure like to make "Part II" required reading also!

This thread has been a real thought provoking, eye-opener for me! :banghead:

May 27, 2005, 10:40 AM
I read thru this thread about a week ago and had one of thos "light bulb" moments. I bought a Hi-Power a few months ago and immediately pulled out the 32lb hammer spring and replaced it with a 26lb spring. I also put an Olympic Arms 1 in 16 twist barrel in it cause all I shoot is cast. Long story short after about 100-120 rounds without cleaning the gun gets a little difficult to go into battery. This is due to bullet lube and crud gunking up the little recess in the breech face where the hood locater pin "thingy" goes. After reading this thread I thought just maybe I'm the cause of all this crud because the gun is opening a little too soon blowing the lube back into the slide. I put the 32lb spring back in and now over 200 rounds later with no cleaning everthing is running fine. The good thing about it was since I had polished the sear and hammer the 32 lb spring only added about 1/2 lb to the trigger pull. Thanks for a great thread! Nick

May 29, 2005, 07:09 PM
Finally had time to sit down and try this out. Removed the fps from my Springfield V10 Ultra and started fitting the new one. I noticed that the original fps was strongly beveled. Compared the two so I wouldn't screw things up too much. ;)

The main point was its width. Trimmed some off the left side and it finally slid all the way into place, with the firing pin hole lining up just right. Then I had to raise the shoulder a bit to clear the ejector. Broke the bottom edge to give it just a bit of bevel and things looked pretty good.

Took it to the range this morning. Boy, there seems to be a noticeable difference! For such a small gun, it barely moves. I know the ports help, but don't remember it being so smooth. Ran a few magazines through it, stopping after each to check for unusual wear and found none. After a bit I noticed two, equal marks on the hammer below the marks from the original fps. Looks like it's hitting nice and even. I"ll have to try it some more next weekend. If that looks good........

then my other 1911s may be getting new stops. :evil:

May 30, 2005, 07:03 PM
Excellent news there Crapshooter!

Have ya noticed any difference in your ejection patterns? The first thing that many people notice is that the brass hits the ground from 25 to 50%
closer to the gun than with the bad old stop... :p

Now...Ya wanna really feel "smooth"? Drop your recoil spring down 2 pounds and try it. Except for the extreme-duty beaters, I use 14 pound springs in all my 5-inch guns. Smoooooooooth! :cool:

May 30, 2005, 07:36 PM
Thanks Tuner. I was at an indoor lane and the empties were bouncing off the side wall, so I don't know where they would have landed.

I'll order a 22 pound spring from Wolffs and see how it works. :D

June 3, 2005, 05:37 PM
Just thought I'd let you guys know that you cleaned Brownell's out of their stops and the entire new batch they got in (81 pieces as of 6/3/05, Brownell's said their order came in May 28th) are all cut for 70- AND 80-series 1911's. If you have a 70-series, you should go directly to EGW to get one, either they sent the wrong ones to Brownell's or Brownell's ordered the wrong ones. They're ugly as sin on a 70-series. :(

Also, the picture at the Brownell's site is misleading on the -001 part. The image looks like untreated steel but they come blued or with a black oxide finish (actually I think the -058's have a black oxide finish).

I'm sending my FPS straight to EGW to have it exchanged with a 70-series stop. After George sees the Brownell's tag on the bag he says he'll try to straighten it out with them.

June 3, 2005, 06:33 PM
I just ordered 6 S-70 type stops directly from George. They were a little rough around the edges...looked to me like a dull end mill was to blame, but a few licks with a smooth mill file cleaned'em up slick as a button. Haven't done anything else except cut the radius and put'em back in the drawer
to await assignment.

I sent one to a guy on another forum to fit to his chopped pistol, and he reports that it's like shootin' a different gun. Smooth cycle...Brass falls in a neat pile...Less muzzle flip and gets back on target quicker...An altogether worthwhile tweak, sez he...and he's gonna put one in all his pistols. :cool:

ken grant
June 3, 2005, 07:46 PM
Wish George would make some stops in Stainless Steel for Series 80's. Sure could use some for my Colts :confused:

George Smith
June 8, 2005, 12:32 PM

If the Sig GSR line starts up again in July or Aug. We can make some SS EGW OS Stops using the same materials. We will have to wait and see if a new PO is forthcoming.

Thank you all for the great post,
and thank you for the work


June 10, 2005, 10:18 PM
I spent a chunk of time today reading this thread and then took a look at the FPS on my Dan Wesson. It's WAAAY relieved and rounded (and consequently, I noticed today a tad loose and starting to slip down and drag on the frame on one side). I had switched to a stiffer recoil spring to calm my insane brass ejection, but I'm beginning to think that a properly fit FPS would do me more good and protect my frame from unnecessary battering in the long run.

So, George at EGW got my order today. :)

I wanted to take the opportunity to thank Tuner, Fuff, Riley, and everybody else for the info in this thread. This is honestly something I NEVER would have thought of with regard to my brass flying 15' to my right. For that matter, it might have been a while longer until I noticed the slightly loose fit of my FPS, but since this thread got me looking at it I noticed it while it was just a little rubbing rather than having actual damage to my frame.

thanks again for the great info folks,


June 10, 2005, 10:51 PM
You're welcome. We live to serve. :D

July 25, 2006, 01:15 PM
Hi everyone, very interesting thread and modification. I will be trying it out as soon as I get the stop from EGW.

Would someone be so kind as to post a picture of an EGW stop with a radius that is appropriate for a 5-inch .45 shooting factory loads? I remember reading that the radius can be adjusted differently for every type of 1911s intended use and am not sure what would be most appropriate for me. I have some confidence in my filing skills and I am going to try and free hand it, and I need an image to compare my stop with so I know when I'm done.

I saw the pictures earlier in the thread, but they don't give me quite enough to go on. If I could see a side view it would let me see the angles of the radius better.

July 25, 2006, 08:12 PM
Most certainly. NYCMedic over on did his first one about as well as I've ever seen one done I swiped his picture for ya.:scrutiny:

I use a slightly smaller radius for mine. This one is probably as close to the original .078 as you'll get it with a file and stone.

July 25, 2006, 09:48 PM
Perfect, per Canuck-IL's advice I will try to track down some sandpaper to do it with for more control. That is a very small radius indeed. What is the purpose of the small radius vs. the square edge that comes from EGW? Does it give the firing pin stop less "bite" into the hammer making slide movement require more mechanical energy?

July 26, 2006, 12:00 AM
...will be sharp enough to wear on your hammer. If it's MIM, like my old SA Champion, it could clean the hammer right off with hot enough loads. I shot it about 100 times like this, and there was a definite mark in the hammer. I radiused it very slightly, and the wear ended there.

July 26, 2006, 12:12 AM
Slowing the slide. We have had a few discussions of the effect of recoil springs on slide recoil speed and also about hammer spring weights as an addition to this effect.
The conclusions were that slide mass has the greatest effect on the initial travel speed and that spring weight had little to do with initial slide speed. The higher the recoil spring weight outside the factory spec., the higher the felt recoil because the spring ties the slide to the frame and as weight goes higher it tends to absorb less and transfer more recoil to the frame. The recoil spring is much more a feeding spring than a major impact on initial slide movement although it does serve to slow the slide as it reaches the end of it's travel and the spring's force increases to rated weight.
A simple way to quantify the effect of a more sharply radiused slide stop would be to measure the difference in length from the hammer pivot point to the two points of hammer intersection between the two stops and then multiply that by the hammer spring rate, which will be far less than the rated weight at the point of initial movement. I would be surprised if it amounted to one tenth of an inch.
To get an idea of the forces involved measure the base of the .45 ACP case, compute area and multiply this times 20,000 PSI. The number will surprise you and this is the number we are working against with springs and mass. You will find that springs are a small factor when compared to mass in controlling the initial slide acceleration. Otherwise we could build pistols with very light slides and stronger springs and end up with lighter weapons. This hasn't proven to be the case.

July 26, 2006, 03:44 AM
As I have said before, a properly sprung 1911 pattern pistol will fire and eject just fine with NO recoil spring at all.

The fired case will land in the same area as they did with the recoil spring in place.
The cases will not be bulged.
There will not be a more prominent ejector mark.

I agree that the name should be changed from recoil spring to slide return spring.
Can we get a Constitutional Admendment?

July 26, 2006, 06:30 AM
Well...Here we go again. Rather than use bandwidth with calculations, I'll try to explain the "why" part of how this thing works like this.

Felt recoil in the autopistol is in three distinct phases. The three events occur so close together, that they seem to be one.

Phase one is the actual recoil...the "kick" of the cartridge firing. That one can only be reduced by changing ammo jungle increasing or reducing slide mass. It is what it is.

Phase two is the effect of the recoil spring providing its own "Equal and Opposite" push between the moving slide and frame. The heavier the recoil spring, the harder it pushes the frame into the hand. The slide's velocity rearward also plays into the total effect. The faster the slide accelerates,
the more sharply the secondary effect of a given spring's loading will be felt.

Phase three comes from the slide impacting the frame at the end of its travel. The harder the slide hits the frame, the higher the gun flips
on impact. Hence, the less slide velocity that is available for that impact, the less the gun will flip. Also hence...the slower the slide accelerates with a given recoil spring, the lower the recoil spring's effect will be during the secondary recoil.

The smaller radius reduces the slide's mechanical advantage in overcoming the
mainspring, thereby delaying the slide's initial acceleration during phase one.
Think of it as tapping the brake at the instant that you nail the gas pedal in a drag race. The elapsed time at the end of the race will go up, while the terminal speed in the traps will drop. No matter how hard the car accelerates
after the brake is released, it can't make up for the lost time and momentum.
If two cars that are theoretically identical...the braked car will lose every time.

In the case of the modified firing pin stop, the effect on felt recoil comes mainly in the tertiary phase...reduced muzzle flip when the slide hits the frame. It seems to be one of those things that fit the category of the whole being greater than the sum of the parts. The only suggestion that I can make is to try it for yourself. The proof's in the puddin' so they say...and arguing the point further won't convince anyone of anything until they give it a whirl.

July 26, 2006, 07:09 AM

Wasn't the small radius the original design?
Didn't the large radius we see so much today originate with the Colt Gold Cup in order to get it to better digest the "softball" 185gr target wadcutter ammo?

The first big radius I ever recall seeing was on a .38 Special Gold Cup.
Up until then all I had seen was the old GI type.
I can't recall which my Father's first year Commander had.

July 26, 2006, 09:33 AM
Howdy Bear,

The stop was changed by the Army Ordnance Department after receiving complaints from the cavalry that the gun was too difficult to hand-cycle with the hammer down...and it is harder to do...which will provide a clue as to its effect on the slide's initial acceleration. Once the hammer is slammed rearward, the effect ends.

July 26, 2006, 09:43 AM
Otherwise we could build pistols with very light slides and stronger springs and end up with lighter weapons. This hasn't proven to be the case.

One thing that has always struck me is how light Glock is able to make the slides (I am making a big assumption that much of the weight is in the slide) on their guns and how light they make them in general. They seriously undercut even the polymer competition by 6 or more ounces for quite some time. The closest I have seen is the new S&W M&P which weight 24 oz with no magazine. The 17 is 22 ounces and the 26 is 19 ounces, and the 21 is 26 ounces. Do Glock slides weigh the same as everybody elses, say a 1911?

Old Fuff
July 26, 2006, 10:25 AM
Glock, like most other later automatics, use a cam on the barrel to control the dwell time - the time that the barrel and slide are locked together. By changing the cam surface dimensions the dwell time can be leghtened or shortened. Browning's link design works fine for its intended purpose, but one can't do much to adjust the dwell time, although some makers try by fooling around with the recoil spring. Within reason, if you can lengthen the dwell time you can lighten the mass of the slide. To my knowledge this was first done in the Browning Hi-Power in 1935.

Walt Rauch
July 26, 2006, 11:02 AM
I learn something everyday. thanks all.

July 26, 2006, 11:28 AM
It is interesting to examine the way factory engineers control slide speed with mass in the Browning style tilting barrel recoil operated pistols. Note the difference between the BHP in 9mm and .40. Heavier slide. H&K 9mm and .40. Heavier slide. Given identical guns within a group, one will almost always find that the engineering solution to controlling slide speed as bullet energy goes up is to increase slide mass. Colt chose not to do this with the Delta and ran into problems.
There is obviously a working range of weight and spring that is acceptable for a given energy. A 1911 in 9mm or .45 ACP will work with near identical springs, but the 9mm will have an easily felt slower slide movement. Colt's early solution was to introduce lightening cuts in the 9mm slide.Some people mistake the heavier spring in a heavier slide as a resistive effort at slide speed, but it is used to control the deceleration of a heavier or faster mass at the end of the recoil stroke.
If anyone has a Glock and 1911 and an accurate scale I think you will find the two slide weights very similar in .45 ACP caliber.

Old Fuff
July 26, 2006, 11:53 AM

Part of this has to do with the fact that a larger cartridge (.45) usually requires a higher, and possibly wider slide because of the cartridge head size. But whatever weight advantage might be gained is lost if the slide is shortened to make a compact or sub-compact pistol unless other modifications are made to the shorter slides.

In his original link-based designs, Browning used the mainspring, hammer, and firing pin stop radius as an additional buffer on the slide. During the early 20th century it was not uncommon for individuals using the 1900 era .38 Colt's to cock the hammer before loading the first round into the chamber, and then lower the hammer on the chambered round. As Tuner noted, the Army didn't buy this for long with their new 1911 .45 pistols, but the design was good enough so that the pistol usually stood up to years of hard service.

During the development of the original Detonics pistol is was discovered that the slide - shortened by 2" from a Government Model - had a slide velocity that was increased by as much as 50%. But oher factors were at work besides lighter slide weight, including a shorter dwell time caused by the barrel dropping at a sharper angle.

July 26, 2006, 12:08 PM
Understood, but it is undeniable that modern designs use slide weight to control slide speed across the board. Compacts will be seen with thicker slide cross section than their full sized counterparts. The 1911 is a poor example of this, because the compacts keep the same cross section, but it is obvious that reliability suffers as slide speed increases due to lower mass.
In the case of Glocks, longer slides have lightening cuts to retain the same mass as standard sized slides. SIGs and H&Ks will be seen with thicker cross section through portions of the slide as the energy of the round is increased. Beretta quickly discovered reliability problems in previously very reliable pistols if slide mass was not increased in the move up from 9mm to .40. Rim diameter doesn't mean much, since almost any slide is wider than common rim diameters. Energy is the key and will have the most effect with respect to slide mass and velocity.

July 26, 2006, 12:13 PM
I haven't gotten the part yet so I can't make any claims as to the efficacy of the modification, but maybe this thread is worth adding to the 1911 clinic.

As an FYI (don't know if it had been mentioned in this specific thread) but S&W 1911s require a series 80 firing pin stop.

July 26, 2006, 01:14 PM

> Given identical guns within a group, one will almost always find that the engineering solution to controlling slide speed as bullet energy goes up is to increase slide mass. Colt chose not to do this with the Delta and ran into problems.<

Colt dropped their candy with the Delta when they missed the opportunity to utilize more of the mainspring's effect by going with a 25-pound mainspring and getting back to the basics on the firing pin stop. Ted Yost and Ned Christiansen figured it out in about two shakes, and I understand that both of these world-class pistolsmiths use a very small radius on the firing pin stops in their Big 10 pistols...and they do it with less recoil spring than the factory standard of...IIRC...22 pounds.

Colt...All it woulda taken is a peek at the old blueprints and for somebody to notice and ask: "Why"

July 26, 2006, 01:32 PM
In the case of the Delta, springs where a bandaid when greater slide mass was clearly called for, and the results were never satisfactory.

July 26, 2006, 02:20 PM

>In the case of the Delta, springs where a bandaid when greater slide mass was clearly called for, and the results were never satisfactory.<

No doubt that the slide could have used another ounce or two...but Ted and Ned seem to have gotten it sorted out in fine fashion...and they're dropping down to 18 or 20 pounds on the recoil spring as a matter of habit, so I hear.
Some of the guys who have tried the combination of small stop radius, 165 PF ammo, and a 23-pound mainspring are reporting short cycles with even 14-pound recoil the effect isn't imaginary.

July 26, 2006, 02:29 PM
165PF is slightly under par for .45 ACP, a full power 10mm is a completely different animal and should have been dealt with accordingly. The 10mm exists in a form close to .40 S&W and any Delta can handle that, but the original full power loading is beyond the normal 1911 capability without some serious mods if the life of the pistol is expected to remain long.

July 26, 2006, 02:43 PM
>>165PF is slightly under par for .45 ACP, a full power 10mm is a completely different animal and should have been dealt with accordingly.<<

I know that 165 PF is light. The reference was made to show that the stop radius does have an effect. Uhm...Maybe you should contact Ted Yost or Ned Christiansen for a full report on how their 10mm pistols do over the long haul. like I said...They seem to have gotten it all sorted out.

July 26, 2006, 02:54 PM
I think they would both agree that a 1911 will live a very long time with 165PF loads and a considerably shorter time with full power 10MM loads regardless of springing or FPS radius.

July 26, 2006, 03:03 PM
As will anything that imparts higher energy and pressure against a breechblock. 38 Special vs .357 Magnum, etc.

What I'm curious about is how the thread went from discussing how using a small radius on the firing pin stop makes a .45 caliber 1911 sweeter to shoot, to how brutal the 10mm is on a standard 1911 frame and slide...about which I completely agree. The slide should have been beefed up.

Maybe you should invest 20 bucks in a stop and a new 23 pound mainspring and try it for yourself...

July 26, 2006, 03:26 PM
You know me Tuner, I'm just not very sensitive to the subtle changes some report with various modifications in spring weights. My first post outlined a simple way to quantify the change.
I guess you could say I don't see a problem to start with and remain somewhat skeptical of the actual effect this mod may have. Having seen different people report widely varying impressions of recoil with an identical pistol and ammunition, I am less inclined to trust impressions(my own included) and more inclined to trust hard data.
Lacking hard data in the form of high speed photography, the next best thing might be ejection distance with a pistol fitted with the two different stops firing identical ammo and fired from a Ransom rest to ensure identical hold. I don't argue that the mod doesn't change anything, I only question the amount of change.
I can of course alter ejection distance with recoil spring weight also, but that doesn't imply the pistol is running better or worse as long as function is not impaired. Only that slide speed at the end of the recoil stoke has been altered slightly.
There is also the question of ammunition tolerance, with a given slide weight the lighter spring will allow a wider tolerance of loads to be digested by the pistol.

July 26, 2006, 03:59 PM
Well...The difference isn't really that subtle. Most report a definite change in the recoil charactistics of the gun, while others report only a faster target reaquisition and split times...but sometimes even subtle changes are worthwhile. Every little bit helps...just like with the 10. it's not about making the gun indestructible. Can't do that unless the gun is never fired. It's about prolonging the useful life of the gun. That's why we change recoil springs and lube slide rails. As far as ammo sensitivity goes, I don't see it. My ammo ranges from 230/850 down to 200/750 fps with 16-pound recoil springs...but either will run all my guns with even an 18-pound recoil spring. Only yhe ejection distance changes. The 200/750/18 combo dribbles the brass out at my right foot...but I don't get short-stroke malfunctions. A different gun just might have a problem. Simple matter of dropping to a lighter recoil spring...which also helps tame the effects of (secondary) recoil
on the shooter.

Really though...You should try it. Ya might find that ya like it a lot.

July 26, 2006, 04:12 PM

You can read some of the testimonials here. It started when John Caradimas...from Athens, Greece...was talking about a dilemma that he had.
Not being able to go out and buy a new pistol at a hat-drop, he was concerned about slide to frame battering in his two guns. Hard for him to order shock buffs without help on this side of the big pond...and having trouble with magazine timing with 18-pound recoil springs...he asked me what to do. I suggested one of EGW's stops with a small radius. I cut one for him, including a pre-fit to maximum print specs on the size...and mailed it. I mentioned that he would probably notice a slight reduction in felt recoil, due to the stop's braking effect...and within two days of installing the stop, he started this thread. It took off, and prompted a few others to try it...and they reported the same...which lit a wildfire. George Smith's firing pin stop sales have taken off, and everybody seems happy with the "modification" which is really nothing more than a return to basics. Ol' John Moses really did know what he was doin'. Yeppers, he did.

July 27, 2006, 12:02 AM
Not trying to rain on the parade, but it seems as if most of the anecdotes about this mod revolve around pistols that were not functioning well to begin with or needed a little tweaking to get them perking due to other factors.
I am interested in seeing more input from users who have substituted the FPS on 1911s that were running just fine prior to the substitution. I understand the mechanics and the forces involved, but I have trouble believing that a tenth of an inch difference(or less) on the position of hammer to FPS contact is going to make this much change.
I have the highest respect for Tuner and EGW and would like to see how the average shooter views the change. Sounds like we should have about 100 reports shortly. Thanks again for an enjoyable discussion.

July 27, 2006, 12:18 AM
I havee changed to the small radius stop on 2 pistols. One was a 10mm Delta Elite, which had some issues prior to the change. These have slowly been resolved.

The other was a 5" .45. There was absolutely nothing wrong with the way this pistol functioned. I ignored my father's advice, (if it ain't broke, don't fix it!), and changed the stop. There was only a slight improvement, barely noticeable. This was with a 19 pound mainspring. Going to a 23 pound mainspring made a great deal of difference. Ejected brass does not fly near as far. Firing 230/840 it is very well mannered.

Now that I look back at the experience, I was not actually going against my father's advice. The original firing pin stop was not broke, and they fixed it anyway. I am just correcting their fix.

I examined a Colt Pony .380 the other day, and noticed that its radius is pretty small. So somebody at Colt knows about this. It is a shame they weren't in charge of the Delta Elite production.

July 27, 2006, 12:41 AM
Interesting. Can't say I've seen a stock 1911 fling brass too far with standard loads, but on the other hand I don't want them dribbling out. I've also heard a lot of people using a 14lb recoil spring and 19lb hammer spring and proclaiming the pistol shot quite a bit softer. Subjective opinions seem to vary widely.

July 27, 2006, 01:07 AM
I am interested in seeing more input from users who have substituted the FPS on 1911s that were running just fine prior to the substitution.
Tuner has installed dozens of them in pistols that were running just fine.
It was done to soften recoil.

I understand the mechanics and the forces involved, Obviously you don't.

...but I have trouble believing that a tenth of an inch difference(or less) on the position of hammer to FPS contact is going to make this much change.It's a matter of leverage NOT a matter of distance. :banghead:
Don't you find it easier to rack the slide of ANY 1911 Pattern pistol if the hammer is already cocked? Of course you do.
If you install a stock, unmodified EGW firing pin stop with the lower edge square just like they send it to you, it is dang near impossible to pull the slide back with the hammer down.

July 27, 2006, 05:08 AM
"It is a matter of leverage NOT distance."

In this case leverage would be calculated by the distance from the hammer pivot point and the intersection of the FPS and hammer. So the difference between the standard FPS and the modified FPS is the difference in distance from the hammer pivot point to FPS at hammer intercept. That is leverage. Can you calculate a numerical difference?
I can't break out the calipers right now, but my rough guess is about one additional pound of spring force.
Please correct this if you think I'm wrong with your figures.

July 27, 2006, 06:05 AM
Jungle, mah fren...The only suggestion that I have is that ya get one and see for y'self. I'd say that a .060 radius...a fresh 23# mainspring...and a fresh 16# recoil spring would do it.

Bear is correct. Try though I might, I can't seem to keep an EGW stop on hand here. Every time I show it to somebody on the range, the reaction is invariably: "I want one!"

All my instincts are tellin' me that this resurrected thread probably needs to go to bed...:scrutiny: but I'll try this instead:

The increased leverage probably doesn't add much more than an extra pound or two of resistance...that's a fact...but it's not the amount of extra force applied so much as WHEN and WHERE it's applied. In this case, it's at the inception of recoil, when the impulse is highest. As you are doubtless aware, about 90% of the energy imparted to the slide is at the instant of firing. It's right there that the hammer offers resistance, since the recoil spring's resistance at that stage of compression is relatively small.

Go back to the drag race mentioned earlier. Would a one-second brake application have more influence on slowing the car at the very beginning of the race, when the car has just started to accelerate...or near the end of the race, when the car is moving at a hundred miles per hour?

July 27, 2006, 07:43 AM
I think it's one small modification worth too!

If there are any left, ;) , I'm going to order one. The worst that can happen is you can't feel the difference and you end up with a spare FP stop...that "ain't bad".

July 27, 2006, 07:49 AM
45Auto said:

>The worst that can happen is you can't feel the difference and you end up with a spare FP stop...that "ain't bad".<

That's the spirit, lad! It's a system, so be sure to start with fresh springs.
23# on the mainspring...16 for the recoil spring.:cool:

July 27, 2006, 09:28 AM

I use a 19.5 lb mainspring now, but I'll try the 23lb also.

Since I shoot "moderate" loads, maybe 170 PF, I do use the 14lb recoil spring which I find "sweet" in overall operation. I'm looking for the FP stop to "hedge" some recoil to the frame, among other things, while using lighter recoil springs.

What do you think?


July 27, 2006, 10:56 AM
With that PF, the 14-pound recoil spring should be fine. The 23# mainspring is also a good idea. Let us know whatcha think...

July 28, 2006, 09:49 PM
Sorry it took a while to get back, but I did get a few measurements and did a few simple calculations to illustrate the effect of this modification.

First, a few basics. The 1911 will fire and eject just fine with no recoil spring. The force applied at firing is a momentary impulse of about 1300 lbs. To find this take the area of the cartridge base and multiply by the pressure. This is difficult for most any spring to resist at least for the initial travel-slide mass controls slide speed during the initial stages of recoil. The bullet moving at 830 FPS causes an equal and opposite recoil of the slide and barrel at about 24 FPS, with the slide mass being decelerated by the recoil spring at the end of it's stroke.

Now, what part does the hammer play in all of this? The hammer acts as a lever against slide movement through the force of the hammer spring. And how much force is applied? We will measure in inch pounds. The distance between the hammer pivot point and contact with a standard slidestop is about .540 inches. The 23 LB hammer spring is at about 60% of it's rated weight with the hammer at rest. So, 13.8/.540=25.55 inch pounds.
The small radius stop is contacting the hammer at about .532 inches from the hammer pivot point. So, 13.8/.532=25.94 inch pounds.

The difference is .39 inch pounds. About the same force it takes to flip open the cap on a tube of toothpaste.

Maybe old JMB knew something when he approved the "new fangled" FPS.

High speed film shows the slide's movement will slap the hammer out of contact with the slide on firing. When you hand rack the slide the hammer will maintain contact with decreasing force as the FPS rides up the hammer.

I hope you enjoyed this quantification of the matter being discussed.

Any comments? How about you BluesBear? Would you like to demonstrate your understanding?

Old Fuff
July 28, 2006, 11:38 PM
Any comments?
I am reminded that some mathematician is supposed to have proved, through careful calculations, that it was impossible for bumble bees to fly … :eek:

Once upon at time gunsmiths building target pistols on the 1911 platform would cut a radius in the bottom of the hammer face, so the only part left was that which impacted the firing pin. They would also radius the firing pin stop more, even to the point of making it a bevel rather then a radius. The purpose of this was to eliminate the buffering effect of the hammer so that the pistol, firing powder-puff target loads, would cycle easier. The modification was particularly popular on .38 Special and .22 R.F. conversions.

In this kind of application the modification worked well. However if you took and fired regular .45 ball ammunition in such a pistol, slide/frame battering would soon appear at the rear of the recoil spring tunnel, and if one kept it up the usual result was a frame cracked through the rail at the slide stop cut-out. Consequently these pistolsmiths did not make this change on pistols intended to shoot full loads. They may not have been math whizzes but they knew what worked, and what didn’t from experience.

While the slide may (or may not) kick the hammer back, contact with the firing pin stop will remain the most at the lowest point. As Tuner has pointed out, the “firing pin stop effect,” to the degree that there is one, happens as the slide is starting to move. It is at this point that the recoil spring – regardless of its weight – has the least effect.

Obviously this modification isn’t for everyone. Neither is any other of the sundry modifications inflicted on this pistol. But many who have tried it have found it to be beneficial, particularly when the platform is pushed to its limits – as in those chambered to use the 10mm cartridge in its heavier loadings, and heavier recoil springs are not the answer.

One of the advantages of this experiment is that it is relatively inexpensive, and the part itself is of excellent quality. Since there is no radius to start with, one can use whatever kind they like. I would note that the radius specified by Tuner comes close to the one originally used by Browning. Once up on a time someone introduced JMB to an Army officer, who called him an “engineer.” Browning then pointedly commented that, “no he wasn’t an engineer, he was a mechanic.”

I don’t think Tuner is an engineer either … :cool:

July 28, 2006, 11:53 PM
Being the excellent historian you are Old Fuff, I am sure you can tell us that JMB approved the modification that changed the parameters of the original FPS.

Exploring the measurable mechanical effect of a modification seems to work better than vauge and unreliable feelings or subjective impressions. I am neither for or against, just wanted to show the actual net effect. Have you any actual measurement you wish to share?

July 29, 2006, 12:01 AM
Maybe old JMB knew something when he approved the "new fangled" FPS.You are misunderstanding. Browning designed and built the 1911 under contract and in cooperation with the Colt's Patent Firearms Manufacturing Company. Once it was accepted by the US Army Browning was out of it. It was Colt's who respecified the firing pin stop at the insistence of the US Army.
The Army said it was too difficult for a big strapping calvaryman to hand cycle the slide with the hammer down. So Colt made it easier.

Now forget about math for a minute. If that simple change made it easier for a human to cycle the slide with the hammer down just think how much easier it then became for the cartridge to do the very same thing.

Jungle has a predispoded opinion and is trying to use Algebra to prove himself right.
Classic misdirection.
What you need is Geometry and Physics.

And common sense.

Go ahead try it. Buy a $15 EGW slide stop and try it. If then you don't agree with us, I'll personally buy it from you for twice what you paid for it.

Go ahead, put your money where your mouth is. Change the stop and then try and tell us that it doesn't require more energy/force to retract the slide with the hammer down. You don't even have to fire a shot.
Until you experience the physical results anything else is just an unproven theory anyway. You want proof so prove it.

Jungle all you have is a theory (and a strong prejudice).
The rest of us have physical experience.

WE understand.

July 29, 2006, 12:12 AM
Perhaps your "understanding" is based on your own unproven feelings.

Let's take the example of a Baer 1911, which many observe to be very tightly fitted in lockup, and very difficult to rack by hand. Yet, wonder of wonders, it functions perfectly. Hand racking and how the pistol behaves under the dynamic conditions of actual firing are two entirely different things. The actual forces generated by firing a live round are stronger than many are aware of, and it boils down to momentum to control this force.

Like I said, I'm neutral on this, and if you can demonstrate that less recoil is generated through some simple practical experiment I am all ears. Even though dynamic forces are different than hand racking, you could rig a trigger pull type measurment of manual racking force and actually demonstrate that difference. How much exactly would that be? And how much effect would that have against an initial 1300+LB momentary impulse?

I have no prejudice, indeed I would like to see this work, my only question is how does it do so.

Show me how .39 inch pounds is going to make a measurable difference.

Just one more thing, can you point me to the documentation that shows Colt modified the design without any input from JMB?

July 29, 2006, 12:25 AM
My feelings have nothing to do with it. I'm talking personal experience and you're spouting conjecture.

You just don't/won't open your mind.

It's YOUR feelings that are the problem.

It has nothing to do with how tight or loose a gun is fitted.
Take a fully functioning 1911 pattern pistol. ANY brand. It' doesn't matter.
Baer, Wilson, Colt, Norinco, Rock River, Rock Island, Kimber or your brother-in-law's dremeled Essex/Llama.
Install a new small radius firing pin stop as detailed above. And then try and tell us that the force/energy needed to cycle the slide is not greater.

You know. You're not really even listening. All you want to do is argue.
From now on you can argue with yourself because this is all I'm going to be seeing. This message is hidden because jungle is on your ignore list. :neener:

You just are no longer worth my time.

July 29, 2006, 12:48 AM
All I know is Im pretty new to 1911's, and this is a topic you can learn somethings from. Like for instance, I know what that doowhatchee majigger is called that cocks the hammer :D

....Ive also learned, if you have problems with a 1911, see

July 29, 2006, 01:07 AM
All I know is that Tuner has never let me travel down the wrong path. My Springer has been 100% reliable, due to Tuner. I have the EGW firing pin stop,this has been the best modification on my gun period.:D

July 29, 2006, 01:16 AM
Seems like something I might want to try on my S&W.

July 29, 2006, 08:34 AM
Lordy mercy! Are we still arguin' about this?:D

I started using the small radius because it was a good way to reduce frame to slide battering without the drawbacks of a heavier recoil spring...and I noticed that one of the secondary effects was that the muzzle flip was less sharp. Further testing revealed that the reduction was due to the slide's impact with the frame...the tertiary recoil...rather than in the actual firing-induced "kick". It made sense, so I took it a step further and shot a gun with
shock buffers to see how much difference in buffer life the stops would make. It made a noticeable difference, with the buffers lasting about 20% longer when used with a 1/16th stop radius. I found that I could even get the buffs to last a bit longer with 14 pound recoil springs and the small radius as opposed to 16-pound springs and the now standard 7/32nds radius...and I knew that I was onto something.

Then I started paying closer attention to the performance of the gun in quick target aquisition on follow-up shots...and it, too was signifigant....especially with lighter than standard recoil springs that reduced the spring's secondary
effect. Simply put, the gun just doesn't "whip" as hard when the slide smacks the frame. Some notice an immediate difference in the way the gun cycles, and others don't really notice it until they shoot with a timer on fast, multiple targets. They don't have to fight to get the gun back down, and some have even had to retrain to prevent throwing their followup shots low.
One guy said that he didn't really feel much difference, but noticed that when his smallish 12 year-old daughter fired the gun, that the muzzle didn't flip nearly as much in her hand as before...rising only to about 30 degrees as opposed to nearly 60 degrees with the 7/32nds stop...with no other changes.

Jungle...I realize that you don't see how this can be, and all I can suggest is that you try it for yourself and see if the gun isn't noticeably more "pleasant"
to shoot with full-power ammo. It's not a simple matter of a small amount of extra resistance. It's WHERE that extra resistance occurs that makes the whole exceed the sum. Putting the brakes on the slide just as it starts to move will do more to reduce its terminal velocity than adding resistance near the end of its travel.

And remember the Bumblebee and all those smart engineers who have proven that it can't fly...and ol' Bob the Bumblebee just nods, shrugs...and flies away.

July 29, 2006, 08:51 AM
Jungle wrote:

>Let's take the example of a Baer 1911, which many observe to be very tightly fitted in lockup, and very difficult to rack by hand.<

Another misconception that exists is that the gun is "Locked up tightly" when
it goes to battery. When static/in-battery, the gun isn't "locked" up. It's held in battery by the recoil spring's tension, and...if tightly a wedging action provided by the lack of clearance between the barrel hood and locking lug faces...and the lower barrel lug/slidestop pin/ upper lug vertical interface...but the gun is not locked. It locks when it fires, and unlocks when the bullet exits. And...yes...The fact that the gun is more difficult to hand-cycle from in-battery does have a small effect. Anything that CAN have an effect on the slide's movement WILL have an effect on the slide's movement. In this case, the effect is even shorter-lived than the hammer's because the hammer offers resistance for a longer time.

July 29, 2006, 09:16 AM
I think the mathematical proof is missing an item. The height at which a pivoting mass is hit.It takes much less effort/time to tackle by hitting the knees first than hitting with the initial impact at the ankles.

July 29, 2006, 09:17 AM
Those of you who would like a very good read on 1911 dynamics may find this helpful:

July 29, 2006, 09:30 AM
Ah! The Venezuelan Rocket Scientist! Sorry...I get lost within the first few paragraphs when I read his stuff. he goes a little too far off on the tangent for my simple mind to follow. Jungle, mah fren...I ain't much of a mathematician, and I sure ain't an engineer...but you're still tryin' to use a straw man to disprove something that too many people have experienced first-hand. Hell...if I had a spare stop here, I'd cut one and send it to ya along with the recoil and mainsprings so you could try it...but I can't seem to keep one on hand. Soon as i get a few, somebody's beatin' on my door for me to fit one to a pistol for'em.

July 29, 2006, 09:42 AM
Thanks Tuner, but I've got all the parts I'll ever need. If someone feels a change with a given modification that's great. I am just trying to quantify what we are dealing with. This is not to challenge you or anyone else, just to present another viewpoint.
Tuner, you are extremely helpful and know more about the 1911 than I ever will and as I said, I am neutral on this but enjoy pondering the how and why. Please don't take it the wrong way and understand I have the highest respect for your knowledge on things 1911.

July 29, 2006, 10:06 AM
Awwwwww...C'mon Jungle! Ain'tcha the least bit curious to see what it's all about?

Remember the wisdom imparted to us by the late, great Yogi Berra:
"In theory, theory and practice are the same. In practice...they ain't.":cool:

Another one is:

"When the calculations don't agree with the results of the experiment...go with the results."


The "modification" is actually a return to the original FROM a modification done by the Army Ordnance Board...and I doubt that Browning had any input, other than maybe a phone call to ask him if it would hurt anything. He probably answered: "Sure. it's your pistol. Do whatever ya want." By that time, he had already moved on to other things, and it didn't likely make much difference to him one way or another. By the way...Check out an original WW2-era High-Power, and you'll see the same 5/64ths radius on the stop.
Interesting...Browning doubtless knew of the AOB's modification, yet he stuck to his design on that point, even on the lighter recoiling P-35. Don't know about anybody else, but I have to defer to JMB on such things. Many people can't seem to accept that he knew more about his design than anybody alive today.

Matt G
July 29, 2006, 10:56 AM
Tuner, you've got me interested.

Sad, but I just now discovered this thread.

Can't claim that I read it all, as I skipped from page two to page... 8!?! Good heavens.

The concept escaped me for a few seconds, but now makes some sense... as a possibility. That said, it looks like a cheap, non-permanent way to attempt to improve a pistol's handling, that can be proven or disproven in a matter of a couple of magazines, without harming (that I can see) the pistol.

The only increased wear that I can possibly see is on the (utterly replaceable) mainspring, which probably is suffering more wear right now by sitting in my lockbox in cocked-'n'-locked condition. :)

Hokay. I'm gonna try it. I'm in love with my 1911, and shoot it quite well, but it's still a .45, and I do shoot full-house loads in it regularly. Perfect double taps are a joy to behold, as are same-hole controlled pairs. Why wouldn't I want to make my 230g loads feel like 200g loads? :confused:

Tuner, can this be done at distance? (Say, by sending my existing F.P. stop?)


Matt G
July 29, 2006, 10:59 AM
Why did the AOB change the radius? What was the intention?

July 29, 2006, 11:04 AM
Howdy Matt. The change was effected in response to the cavalry personnel's complaints that the gun was too difficult to hand-cycle in a hurry
with the hammer down...which was the required method of carry unless action was iminent. Problem with that was...sometimes iminent action didn't give a helluva lotta warning. The "cure" was to cut a larger radius on the stop to raise the stop's contact point on the hammer, and increase the mechanical advantage in overcoming the mainspring. And the mainspring won't wear any faster than with the 7/32nds stop radius. You do, however, want the radius to contact the hammer straight across, or it'll throw a side-load on the hammer pin.

Check your PMs...

Old Fuff
July 29, 2006, 11:56 AM
Just one more thing, can you point me to the documentation that shows Colt modified the design without any input from JMB?

The U.S. Army adopted the Colt .45 pistol on March 29, 1911 when the company received the following notification:

I am instructed by the Chief of Ordnance to inform you that the Colt automatic pistol, caliber .45 tested at the Springfield Armory beginning March 15, 1911, has passed the prescribed tests and has been adopted for the service in place of the Colt Army Revolver, caliber .38.

Lt. Col. John T. Thompson.

Following this notification Colt was issued a production contract, and John Browning passed out of the picture, except to receive royalties on his patents. His job was to design the pistol, and that phase was finished. Thereafter any discussions or orders to make modifications were between the prime contractor (Colt) and the Ordnance Department.

In January, 1918 at about serial number 240,000 the radius of the rounded edge on the bottom of the firing pin stop was increased from .078R to 7/32R. This permitted easier cocking of the hammer by recoil of the slide. The change was initiated by Colt.

Colt.45 Service Pistols; C. W. Clawson.

July 29, 2006, 12:22 PM
heh. 1918, Browning was up to his neck in so many other things that he probably hadn't even seen a 1911 pistol in five years.

July 29, 2006, 12:31 PM
Tuner where can I get one of those stops ?

July 29, 2006, 12:35 PM
Tang...You can order from Brownells or direct from EGW. Be sure to specify
Series 80 or pre-80/70 type. They're oversized too, so fitting is required.

July 29, 2006, 12:48 PM
I assume my S&W is series 80 ?

July 29, 2006, 12:54 PM is.

Old Fuff
July 29, 2006, 01:04 PM
heh. 1918, Browning was up to his neck in so many other things that he probably hadn't even seen a 1911 pistol in five years.

Exactly. John Browning made his fortune (and a sizeable one) by designing guns and patenting the key features. Then he would go to major manufacturers (Colt, Winchester, Fabrique Nationale, etc.) and lease them the right to use his patents in exchange for a royalty to be paid on each gun made. In the case of the Government Model of 1911 he went further and worked with Colts in designing and perfecting a new service pistol for the U.S. armed forces. He knew darn well if the Army adopted the Colt pistol (which they did) and he got a cut on each gun made, plus a piece of Colts commercial production (including foreign military contracts) hed be rolling in bucks. If Colts and/or the Army wanted to make changes he couldnt care less so long as they paid him his royalty. If they wanted advice he was always available as a paid consultant. :cool:

He wasnt after all in the business for fun and grins :evil: :)

July 29, 2006, 02:56 PM
I'm gonna post pictures later on to show how much lower the contact point is on the hammer. it's more than a tenth inch...much lower. I even dug up an OEM stop from an older Colt Commander that has a 1/8th radius on Colt was aware of the effect that it had. Why they didn't use it on the Deltas is a mystery. They went to 7/32nds across the board by the time the Series 80 pistols made their debut. I use a smaller radius than the original .078 inch (5/64ths) on 5-inch guns to get the full benefit. Officer's Models get a 1/10th radius, and I normally go with a 5/64ths on Commanders that I don't own and can't control what recoil spring that the owner may use. All my Commanders get the .060 radius and a 16-pound recoil spring.

Gotta wait for Kelie to wake up so she can run the camera. She did a 7P-7A shift in the ER last night, and if I wake her up early to make gun pix, ya'll are gonna hafta find another tuner...:D

ken grant
July 29, 2006, 03:11 PM
Tuner did a FPS for in a Norinco Compact and the first trigger pull with ammo showed me a great deal of recoil feel difference.:D
Some people would not believe such a small change could have such an effect.
It doesn't matter if it really makes a difference or not----what matters is the fact that if you THINK it makes a difference---IT DOES!!!!!!:what:

July 29, 2006, 03:56 PM
Ken...Ya coulda gone all day and not said that!:neener:

Old Fuff
July 29, 2006, 05:10 PM
Gotta wait for Kelie to wake up so she can run the camera. She did a 7P-7A shift in the ER last night, and if I wake her up early to make gun pix, ya'll are gonna hafta find another tuner...

One mug of turbo-coffee should do the job... :evil:

July 29, 2006, 05:19 PM
Nah. She's built up an immunity to the stuff. She can drink a half-pot and go sleep like she had a clear conscience.

Ken...It ain't got nuttin' ta do with thinkin'. It's physics. Anything that CAN have an influence on the slide WILL have an influence.:cool:

July 29, 2006, 05:44 PM
Recoil operated firearms are a balancing act.
The closer things are to being in balance with each other the better they work.

In fact any machine must be in balance with itself (and it's "environment") in order to work to it's maximum efficiency.

July 29, 2006, 05:46 PM
Tuner, we are all extremely gratefull to you for your down-to-earth teachings and explainations of complex processes.

You are truly a teacher of the highest magnutude.

ken grant
July 29, 2006, 06:31 PM
Tuner,I know that the stop really makes a difference. The point I wanted to make was, If your mind tells you it is different,it is.
A case in point---I used to hate shooting a big-bore rifle(375 H&H,458 Win,458 Lott) They kicked the snot out of me.
While I was in Zaire and used a big-bore on game,the recoil didn't seem the same.
I know nothing changed and the recoil was the same,but my mind told me it was different. Seemed as almost no recoil at all.

July 29, 2006, 07:55 PM
Ken, mah fren...A man never remembers hearin' the report or feelin' the kick when the hammer falls for blood. It's funny, but even without ear plugs, when I'd drop a 10-point buck with a short-coupled .308, my ears didn't even ring.

July 29, 2006, 10:27 PM
The closer things are to being in balance with each other the better they work.

Didn't we learn this from "The Karate Kid"?? :evil:

July 30, 2006, 01:06 PM
Just to sum up some of the impressions. Some have said the change in FPS has had a major effect and some say they can hardly tell the difference. The poster who said it works if you believe is very close to the truth. Sounds like voodoo, but under varying conditions I'm sure our experience with recoil, given the same gun and ammunition has varied. I was interested in the poster who said he didn't feel much difference, but noticed a change in recoil with his daughter shooting. Less mass in the shooter resisting recoil and more absorbing? Limp wristing is known to take more out of the reserves a pistol needs to function.

What would JMB do? Colt initiated the change and it has worked well in the 88 years hence. Was JMB consulted? No proof either way, but certainly some rich historical speculation.

So where does the sensation of recoil come from in this pistol? Primarily from the slide hitting the frame at the end of it's travel at about 15 FPS. What slows the slide from it's initial speed? At the beginning of decelleration, which begins as soon as the bullet leaves the barrel, it is a combination of the recoil spring, hammer spring and friction.

It seems that springs have little effect fighting the initial pulse of 2240 LBS, but become more effective after unlock.

For those of you able to wade through the article on 1911 dynamics it was noted that the recoil spring absorbed about 26.1 inch pounds. The hamer spring was not calculated, but it absorbs about 17-20 inch pounds with the upper figure closer to the small radius slide stop. The remainder of the energy, less friction, is felt as recoil.

July 30, 2006, 04:06 PM
Naw, Jungle. It ain't voodoo. It's physics!

For the record, it was never touted as a "recoil reducer." Its primary effect is to reduce slide to frame impact by causing the slide to lose momentum at the inception of movement...which it does... will vary a little from gun to gun, depending on how slick the slide moves, ammo, recoil spring, etc.

Bottom line though, is....If you're not willing to try it and see for yourself what its effects are, then everything else is speculation and opinion based on
your own belief system.

Oh...And that Tiro guy is a real hoot! I could get to likin' his posts except that they get to be a little more involved than they need to be. One thing I did notice that he was wide of the mark on...He maintains that the hammer cocks smoothly and remains in contact with the slide...which it assuredly does not. I'm sure that there are other things, and I might go find a few if i could find the time to wade through all the rocket science stuff.

Cheers, ya'll!

July 30, 2006, 07:11 PM
Showing the radius on three different firing pin stops.

Centered is an EGW stop with the 1/16th radius that I like to use on 5-inch guns. On the right is a WW2 USGI stop that sports the standard 7/32nds radius. On the left is a stop that was OEM in an early Colt Commander. The radius is just a tick smaller 1/8th inch...I'd estimate it at about .120 or so.
During the same era...around 1968...the stops on the 5-inch Colts were the
now-standard 7/ Colt was obviously aware of the effect.

July 30, 2006, 07:12 PM
A side view of the same three stops. On the right of the EGW is the early Commander stop. On the left is the USGI stop with the 7/32nds radius.

July 30, 2006, 08:06 PM
Interesting. Do you have a measurement of the difference in height between the EGW part and the stock colt parts from the bottom of the FPS to the point it would intercept the hammer?

Here is another article with comparison of the math model to actual high speed photography:

July 30, 2006, 08:23 PM
Jungle asked:

>>Interesting. Do you have a measurement of the difference in height fom the bottom of the FPS to the point it would intercept the hammer?<<

Haven't taken an exact measurement, but the point of contact with the hammer would be the line where the flat begins at the top of the radius.
A machinist's scale would be your best bet.

July 31, 2006, 12:21 AM
Tuner, can the radius be changed on my Commander size gun ? You said something about you use the EGW on 5" guns.

July 31, 2006, 12:27 AM
Tang...Nope. Gotta start with a new, square-bottomed stop from EGW.

Old Fuff
July 31, 2006, 12:45 AM

I think ya' missed on that one. You do indeed have to start with a new EGW firing pin stop, but they can be fitted to any size 1911 platform pistol. You do have to determine if the pre-series 70/series 70 or series 80 is the correct stop to use depending on the pistol.

Remember, only the Old Fuff is perfect... :neener: :rolleyes: :rolleyes: :rolleyes:

July 31, 2006, 01:07 AM
Remember, only the Old Fuff is perfect... Fuff is a Glock?!?! :eek:


Old Fuff
July 31, 2006, 02:34 AM
:cuss: :cuss: :cuss: :cuss: :D :D

July 31, 2006, 08:41 AM
Naw, Fuff...I think he was askin' if the radius could be changed...:scrutiny:

July 31, 2006, 11:43 AM
No actually, I misunderstood. I thought you were saying you could only change the FPS on a 5" gun. Which to my unknowing eyes, made sense, since the slide is shorter on my Commander size gun.

July 31, 2006, 02:08 PM
Okay...Now i've got it! Sorry Fuff. Ya read it better'n I did.:cool:

Tang...Yep. It can be changed.

August 1, 2006, 04:25 PM
I played with different combinations on a fat frame 5" 40 S&W competition gun, took a couple stops and cut them from just a broken edge to slightly less than a stock series 80 stop. With three stops and a factory STI stop, series 80 radius cut on it, I did some testing.

The gun FEELS great with the short radius stop in it, feels much more stable and cuts down the secondary pulse nasty hit by a lot. The shorter the radius the better the gun felt. The front sight stayed planted longer during firing, or at least it seemed like it did. I did not notice that cycling speed was reduced, and it did not seem like front sight dip at slide close changed much if any either. Win/win situation? Problem is that the original STI long radius stop gave me better hits in less time......

Is it just that I grooved the timing of this gun in recoil and recovery over a couple thousand rounds before this test, and that 1000 rounds after deciding the short radius stop was the way to go isn't enough to re-learn the timing? I don't think so, I can generally pick a gun up and get to work with it fairly quickly. The testing I did was fairly quick, couple hundred rounds. Then I put it into competition use, and shot a couple IPSC matches with it. All together I put about a thousand rounds through it with the short radius stop in it. The matches didn't go too well, so I decided to do a little head to head testing with the timer. I think it is that the harsh feel of the long radius stop is what it feels like when all the things the gun needs to do in ejection, feeding, and recoil recovery happen faster. It gets what it needs to do done faster, then I can get to what I need to do faster.

Thoughts? Comments?

August 1, 2006, 04:52 PM
HSMITH, Excellent and interesting test writeup. It makes it clear that altering the dynamics in one area will have consequences in another. All machines are a series of tradeoffs, with the trades made in one area to optimize another.

You didn't say what type of load you are using, but in general the .40 has a more rapid and higher peak pressure spike than the .45 ACP. I found your comments on the various stops very interesting due to using the same pistol and one with which you are quite familiar.

Any comment on reliability, ease of manual racking, or ejection pattern?

August 1, 2006, 04:57 PM
HSMITH wrote...many things.

Your complaint is fairly common. Several of the guys that have used the shortened radius report that they literally had to start from scratch and relearn the way to handle the gun. Almost all have reported that they
had trained themselves to pull the gun out of recoil for so long, that they actually pulled it too far, and slowed down...because they had to bring the gun back UP to reaquire the sights...until they reprogrammed the muscles and nerves to bring it back down to the sweet spot. After they managed that, they sped up. Best WAG is that, like flinching, ya gotta be aware that you're doin' it before you can take steps to cure it.

Try dropping the recoil spring a pound or two and see if that doesn't get ya back on your game.

August 1, 2006, 05:26 PM
Just one other thought. In reading post #190 Old Fuff quotes the excellent Clawson tome.
"This permitted easier cocking of the hammer by recoil of the slide." A comment on the 1918 change to the FPS.
This appears to be at odds with the general opinion that it was done to make manual racking easier. Was it done for reliability as the quote implies or actually to make it easier for those hardy troopers to hand cycle the pistol?

So which is it?

August 1, 2006, 05:49 PM
It was done in response to the Cavalry personnel's complaints that the gun was too hard to hand-cycle with the hammer down. Clawson sometimes goofs, just like a few others have. One publication in particular, stated that the thumb safety was first, and the grip safety added at the behest of the Army Ordnance Department...which is backward. The first 6 prototypes of the 1911 as we would recognize it today...built in 1910...didn't have the thumb safety.

And no...Reliability doesn't come into play. Several of the guys who have tried it report better reliability with the smaller radius. Some of that comes from using a lighter recoil spring, some comes from smoother cycling.

Again...It's a cheap, quick swap. Why-don't-you-try-it-and-see-for-yourself? If you'll order one and have it sent to me, I'll cut the radius and pre-fit the width to maximum print specs and shoot it over to ya..:cool:

August 1, 2006, 06:22 PM
Jungle, racking the slide was a LOT harder, not a big deal though. Loads used were constant through all of my fiddling, a 180 JHP loaded long with a very fast powder. They chrono at 970 most days.....

Yes, it was a gun that I am very familiar with, that is why I hesitated to post what I saw and also question the validity of the results I had. I am curious as to what others have seen. I think I know what happened and what I saw, but I wouldn't put any money on it.

Tuner, I do pull the gun down out of recoil. I know I do, I have seen myself do it LOL. I can adjust from 40 to 45 to 9mm and so on very quickly, so I don't know how much emphasis to put on pulling the gun down out of recoil. Also, the type of shooting I am doing with this gun and the speed that I am doing it at isn't applicable to what most people are doing. The differences in time I am seeing are insignificant for most people too, a few hundredths of a second from shot to shot is all. Even the gun I am working with is not what most people are using, this is a fat 40, bull barrel, lightened slide, 1.5 pound trigger, yadda yadda yadda. It is a purpose built machine for playing gun games, and the shooting games are a whole 'nuther ballgame in many respects....

I did try a recoil spring change, I had a 12 in it and tried a 13, 10 and 11. Ended up liking the 11 and stuck with it for now, with the long radius stop. I could not tell much difference with the short radius stop in between the 10 and the 13, but I honestly didn't give it much of an effort. 20-25 rounds with each is all.

"Don't fix it if it isn't broken" is one of the unwritten rules concerning guns for competition it seems, and that is part of why I stopped testing different things. I don't want to sacrifice performance today, or tomorrow, unless I know paydirt lies ahead and I just didn't get a warm fuzzy about potential gains in performance. It certainly felt better, felt recoil is reduced by a large amount, so I was surprised to see the timer tell me I was slower. It felt like it HAD to be faster, especially with how much more stable the gun appeared to be in firing.

At any rate, I like talking about guns and can't help but fiddle with them....

August 1, 2006, 06:54 PM
Tuner, Thanks again for the friendly offer. I will try one as soon as the pipeline fills back up, and can do the fitting myself with no problem.

One has to wonder why the major makers, semi-custom, and custom smiths haven't adopted this across the board. The concept has been around for quite awhile, they are aware of it-even to the point of using it in a few exceptional cases. So what is the downside? More difficult manual operation of the slide, possibly more sensitivity to the odd light load, and of course the need to bring the mainspring up to 23 lbs and the recoil spring down to 14 lbs to recieve the full benefit. No sweat, plenty of springs around.

Don't fix it if it ain't broken is a written rule for defensive weapons, but in this case there is enough curiosity to try it on the range.

Old Fuff
August 1, 2006, 07:17 PM
So which is it?

The Old Fuff suspects a bit of both. Clawson usually goes into great detail concerning changes, but on this one he simply mentioned it in passing. I too have read about complaints from the horse-troopers, but I'm still trying to find it.

The importance of the cite I posted is that Colt (and obviously the Army) knew that there was a relationship between the firing pin stop radius and slide velocity - at least in 1918.

There is no question that the 1911 platform (excluding sub-compacts) will work regardless of the firing pin stop radius - at least within reason. The advantages of the smaller radius come into play when, for whatever reason, you want to slow slide velocity without going to the ineffective use of heavier recoil springs.

August 1, 2006, 08:09 PM
Jungle pondered:

>One has to wonder why the major makers, semi-custom, and custom smiths haven't adopted this across the board.<

Many of them (Custom builders) have...but most use it on the 10mm pistols so they can drop recoil spring loads without sacrificing the buffering effect when the slide smacks the frame. Heavy recoil springs help buffer the impact stresses in recoil, but make'em worse when the slide goes back to battery. Slidestop cross pin holes in the frames get wallowed out and elongated...Frames crack adjacent to the crosspin hole...Lower lug feet take a pounding, etc. No such thing as a free lunch. Slides have been known to crack at the junction of the spring tunnel, where a sharp corner causes a stress riser. If the small radius reduces impact by 10 or 15%, that equates to either a 10 or 15% smaller chance of a crack or failure...or it extends the service life of the slide by a like amount. Equate it with reducing your powder charges by 10% and it starts to make sense.
(Upping the recoil spring load/rate also makes magazine timing and function more critical because of higher return to battery speeds.)

Again...Buffering impact is the real reasoning behind it. That it also changes the recoil charactistics of the gun is a side-effect, and since no two people grip the gun exactly the same, the resulting "feel" will vary from shooter to shooter.

August 1, 2006, 08:29 PM
So they have come to the conclusion it is neither needed or desirable on 1911s that are not 10mm, or other higher than .45 ACP energy rounds?

Shockbuffs seem to be a more widely used remedy to decreasing the slide to frame impact, and I notice you use them on your range guns.

August 1, 2006, 09:12 PM
>>So they have come to the conclusion it is neither needed or desirable on 1911s that are not 10mm, or other higher than .45 ACP energy rounds?<<

No. I never implied that. You jumped to a conclusion. Some use'em on .45s too. One local smith will use nothing but...even on 9mm pistols.

>>Shockbuffs seem to be a more widely used remedy to decreasing the slide to frame impact, and I notice you use them on your range guns.<<

Nope. I never use shock buffs, and never have very much...beyond curiousity when they first emerged. I used buffs to see if there was any difference in the life of the buffs between the standard stop and the small radius stop. There was. I drew the conclusion that the slide doesn't hit the frame as hard with the small radius stop.

For what it's worth, I think that the shock buff is a solution to a non-issue.
Either that, or an ingenious marketing ploy for the man who invented'em and then convinced some of us that we were destroying our guns without'em.
A little like the Para PXT extractor, the full-length guide rod, and the Tripp Cobra magazine that corrects the "flawed" feed angle. Oh, how DID we ever manage without such things?:rolleyes:


None of my long-term/hard-use beaters suffer any slide or frame impact damage...and two of'em have collectively passed the quarter-million round mark. Back in the days before George Smith introduced his tuneable, square-bottomed stops...when I couldn't find any originals, I made my own. I drink a
toast to ol' George every time I need a few. Instead of takin' hours to make'em up, I just pick up the phone and the mailman brings'em.


Old Fuff
August 1, 2006, 09:24 PM
So they have come to the conclusion it is neither needed or desirable on 1911s that are not 10mm, or other higher than .45 ACP energy rounds?

I'm not sure that too many of our current cop of clone builders and custom smiths know anything about the firing pin stop effect - and care less if they do. Considering the reliability problems that seem rampent in some of their products it would seem that they aren't too knowledgeable about some other things either.

Shockbuffs seem to be a more widely used remedy to decreasing the slide to frame impact, and I notice you use them on your range guns.

Again, relatively few .45/1911 owners outside of this forum are aware that they can control slide velocity to a degree with the firing pin stop. The conventional wisdom is to use plastic buffers, sometimes in combination with stronger recoil springs. As for myself I don't want to buffer the slide at the end of its stroke, when it needs a kick in the butt for reliable feeding. What I do wnat is to slow the slide at the beginning of the rearward cycle. I also don't want to batter the slide stop pin when the slide goes into battery with an over-loaded recoil spring.

Last but not least - over the long hall the firing pin stop will last and be more economical then changing expendable plastic buffers.

August 1, 2006, 09:44 PM
Don't have any use for buffers, but as Tuner pointed out, they can give a rough guide to slide velocity at frame impact when trying different combinations of springs.
Can't really say what the custom builders are thinking, but it was a question not a conclusion.
Don't worry Tuner, you won't have to roll your eyes skyward anymore, I will try it and report back. Well, maybe you will have to roll them skyward again.

Ya'll have a good one, enjoyed it.

August 1, 2006, 09:49 PM
Lordy! Let's put this one to rest...Please!:D

Sorry Jungle. ya gotta admit though...It's a little wearisome havin' to say the same thing over and over again.

When ya try it sure to use a fresh recoil and mainspring. It's a system. Always has been...even with the 7/32nds radius.

August 1, 2006, 10:15 PM
Tuner, I understood what you were saying before you said it. Repetition and counting of cadence was not required. Results have been mixed when reviewed by some VERY experienced shooters, but of course I have faith in your experience. Enjoyed the conversation, as always.

August 2, 2006, 12:57 AM
You can't shine light through a closed door.



You can't teach anything to a person who already knows all.

August 2, 2006, 04:23 AM
Okay I have had enough.... I have been following this thread from the get go. It is simply the coefficient of friction related to surface bearing. Please, I beg you, don't make me do the math. This trick was shown to me around 1983 in a class at Yavapai College in Prescott Arizona from a guy who was a retired USAF armorer. He was the guy that built the guns for the USAF shooting team and what a gold mine I found when picking his brain. God rest John's soul. John was a genius with the 1911 and if God competes with a 1911 in "Divine Shooting Matches" I know who works on his guns. If something is real then it can be proven with math. This can be proven with math and friction coefficients.

Okay layman terms:

You know that one part of the freeway that you really dig driving on because it has sharp turns and it's kind of fun? Now imagine doing it at the same speed with tires 1/8th of the current width and no tread. What happens? You slide off the road missing the turn. That is it in general terms. In order to calculate it specifically you would have to measure or guesstimate Ra on the contact surfaces, measure bearing surface area and throw quite a few Greek alpahbetic characters in a formula to measure and compare the actual forces. Not fun but certainly do-able.

August 2, 2006, 04:51 AM
medmo, That is some math I'd very much like to see, but I can understand your reluctance to share it.

August 2, 2006, 07:02 AM
Medmo...Not bein' an advanced mathematician, I can't dispute it...but it's got more to do with simple leverage than friction. The smaller radius lowers the contact point on the hammer, and moves the force (slide) closer to the fulcrum. (hammer pin) While that'll probably increase the frictional resistance during the hammer's rotation, it's not the primary mechanism in delaying the slide.

Get on a see-saw with a small child. When the fulcrum is in the center, the little'un remains in the air. Move the board to get the fulcrum close enough to you, and the wee one can keep YOU airborne. Leverage.

And...This one's probably best laid to rest. Fatigue is starting to push a few of us some toward a flamefest...and that ain't good. One day, I hope to have Jungle and some others over for a range trip/turbocoffee/BS session and if we get all gnarly over somethin' like this, it'll never happen. I've made a few lasting friends through these forums, and hope to continue the tradition.

And with that...

Goodnight Chesty..wherever you are!;)

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