Small radius firing pin stop for 1911s

[Greg528iT]

The post indicated using MORE than standard..
You are talking about going lighter and then if required going to MORE.. You do not say more than standard.

Every other post on this forum you repeat about NOT having to go to the heavier recoil springs, it's a fix that masks the initial problem.. thus for someone to suggest to move to a heavier recoil spring (from standard) is opposite of your general console.

I am being a bit pig head causes you delete posts. You must have some problem with me pointing out that you are differing from JMB original design. Me personally I THINK that is should be adjust some for today's situations. I am trying to dispel the "It has to be exactly like JMB designed it. It's OK. LOOK even Tuner does it"

 

[1911Tuner]

The post indicated using MORE than standard.

Jim's post was pretty clear. I understood what he meant. If you'll go back and read it again...all of it...carefully...it'll be clear for you, I suspect.

You must have some problem with me pointing out that you are differing from JMB original design.

And I offered a detailed explanation on that, too...or did you not read it?

Condensed version:

I varied from the original radius by .0156 inch and didn't notice any detrimental effect...so I stuck with it. Do you know how small a difference that is?

Why?

Basically because I'm lazy and it's easier and faster to cut a light bevel and roll it on a stone than trying to mill or file a precise radius. It might be a .062 on one... .070 on another one...and it might be .055 on yet another one. As long as it's a small radius, I don't get too tangled up in minor details.

 

[Greg528iT]

Going back and re reading.. I see there is a paradigm shift required.
When I talk about springs or other similar objects I would use 3 distinct terms. Normal, weaker, and stronger or variations to that theme.. ie. stiffer = stronger.

When I read that Jim said he went to a lower (softer, weaker) spring.. then moving to a stronger (stiffer) spring.. Now while the Normal spring is stiffer than the softer spring I was expecting it to say.. "... moving back to the normal spring..." if that is what he meant by stiffer than the soft.
When I read he moved from the softer to stiffer springs, I read. jumping over the normal spring.

 

[Greg528iT]

Why?

Basically because I'm lazy and it's easier and faster to cut a light bevel and roll it on a stone than trying to mill or file a precise radius. It might be a .062 on one... .070 on another one...and it might be .055 on yet another one. As long as it's a small radius, I don't get too tangled up in minor details.

This is more detail than previously given. The type of detail I am looking for.

Since this thread has started, I'm considering picking up a Wilson small radius stop. It's only $19... Once I do, I would look / measure it.. compare.. maybe tinker. My current 1911s are running great, but hey I can always put the original back in.

When I 1st started reading this, my 1st thought was.. would too sharp an edge on the stop cause a fatigue issue for the hammer??? I expect the steel of the stop is soft enough it'll knock the edge off pretty quick, but would the 1st couple shots cause the sharp edge in the hammer that could propagate???? (wondering out loud, as I can't see putting one in, without an eased edge)

 

[1911Tuner]

would too sharp an edge on the stop cause a fatigue issue for the hammer???

No. Ned Christiansen runs the EGW stops in his 10mm custom builds as they come...square. Even the square bottom has a radius. It's just a very small one.

One thing that you do have to look for when you leave one square is that the hammer face will strike flat on the stop. Some aftermarket hammers may contact the square bottom and cause ignition problems. I ran into that once. Can't remember who made/marketed the hammer, but it was one of those skeletonized "racegun" type hammers. A light bevel on the corner set it right.

I expect the steel of the stop is soft enough it'll knock the edge off pretty quick.

They're not really any softer than the hammers as far as I can tell. I've been running the same ones in my dedicated range beaters for years and a lot of rounds, and I can't see any change other than polishing.

I'm considering picking up a Wilson small radius stop.

The advantage with the Wilson is that it's pretty much a drop-in. The radius is whatever Wilson decided on. The advantage with the EGW is that it's oversized and allows the installer to fit it closely to the slide and the extractor...stabilizing the extractor and making ejection more consistent...and the square bottom lets you set the radius as small as you want.

This is more detail than previously given.

It's nothing new. Since the subject of the stop radius first came up here about 7 or 8 years ago, I've always maintained that going for a precise dimension is unnecessary unless the object of the exercise is to exactly duplicate the original...and even that has a +/- tolerance of .005 inch. I'd have thought you'd have run across that by now.

 

[MCMXI]

The Wilson firing pin stop that I linked to in my first post doesn't really have much if any radius at the bottom. The photo on their website is misleading. It was a good fit in my Kimber slide and a fair bit tighter than the Ed Brown stop it replaced. As I mentioned before, Dan Wesson 1911s use a small radius firing pin stop. That might help explain why my V-Bob feels like it shoots softer than my EB SF Carry. That and the difference in recoil spring weight. EB uses a 20lb spring but the V-Bob Wolff spring is 16lb or less. I can see lots of changes ahead.

 

[Greg528iT]

One thing that you do have to look for when you leave one square is that the hammer face will strike flat on the stop

Gotcha. I'll spread some transfer ink and see what the hammer strike surface pattern is.

They're not really any softer than the hammers as far as I can tell.

I was unsure of what the various new parts were going to be made to. Hammers, with the hammer hooks often are sold being from a harder tool steel, for "as they promoted" longer hammer hook wear. When I hear HARD, I think brittle though it all relative of course. Good hard tool steel is not so much brittle like glass but more brittle than lead.

The Wilson I saw said. oversized. How oversized is of course subjective. So the EGW is for sure needing to be fit. Good to know.

This is my 1st foray into firing pin stops. Again my 3 active 1911s run very well. This is about figuring something new out.

 

[1911Tuner]

I'll spread some transfer ink and see what the hammer strike surface pattern is.

You'll probably be able to look between the stop and the hammer face and see if there's a problem. If you can see firing pin, the bottom of the stop is contacting the stem of the hammer before it goes full forward. Use a good light. Unless you use a rooneygun hammer, it won't likely be an issue, and even then only on certain guns. Tolerances stack in the wrong direction sometimes.

 

[Greg528iT]

Yeah, probably be able to see it ok with a bright light.

Looking back at the original picture I see why my brain jumped to the fatigue issue. The stops are all dented by the hammer. The force of recoil being more than that of the hammer falling............. but being in contact when the impulse starts is probably what saves it.

 

[Fred_G]

I have never heard of this. After reading Tuner's explanations, it does seem to make some sense. Would this one be the one to get? http://www.midwayusa.com/product/18...-bottom-1911-45-acp-series-70-stainless-steel

My 1911 is a series 80 set up as a series 70 safety, if that makes any difference.

 

[1911Tuner]

Looks like it, Fred. Probably an EGW. I didn't know that Wilson's came with a square bottom. From what I'd heard...and seen on a couple of Wilson's recent pistols...the stops came with an original-spec radius in place.

Or maybe my memory is failin' like everything else...

If I was a dog, they'd probably wanna put me to sleep...

Remember that Series 80 stops are different than original, or so-called Series 70 stops. Make sure to get the right one.

It's funny. Before the subject of the original firing pin stops and the small radius first emerged, the only pistols that I'd ever seen'em on were original GI pistols made before January 1918 that had escaped the change to the 7/32nds radius stop, and original commercial/civilian Government models of the same era. Now, it seems like everybody has jumped on the bandwagon, with some...like Wilson Combat...installing them as SOP.

Interesting.

I guess they do watch these boards.

And it all got started over on M1911.org after I cobbled one up for the owner and shipped it to Greece. He started a thread on the amount of recoil reduction it produced, and it lit off like a Roman candle. I now see it mentioned on boards that I've never visited.

The originals were so hard to come by that at one point, I was forced to make my own stops so I could use a small radius. I had access to a fully equipped machine shop at the time, so it wasn't hard to arrange. I could set up and cut'em in multiples. Then, when I retired and lost access to the shop, I was forced to use the mill function on a Shop Smith...which ain't exactly a precision setup. I had to leave enough material to finish to dimension with a file...which was a drag.

When EGW stops made the scene, I breathed a happy sigh, because they saved me a ton of work, and I owe George a big thanks.

 

[Fred_G]

Thanks for the info, will look into what series 80 one to buy.

 

[Coltdriver]

I picked up a Colt Compact Officers in .45. Had lots of concerns about making it reliable and figured it was just too much bullet pushing too little slide.

So I read 1911Tuner's advice, installed a 24 pound hammer spring, a flat bottomed FPS and added a full length guide rod (just to add friction) with a flat wound spring.

Mine is a total pleasure to shoot and has turned out to be very reliable. I do run good Colt Magazines.

Between all of the pieces (I very marginally knocked the edge off of the FPS, just smoothed it really) they reduce the speed of the slide movement, give enough time for the mag to push another round into place and just make it easy to shoot with a very noticeable reduction in the snappiness of the unmodified version.

 

[1911Tuner]

Ah! The Officer's Models. They present some unique hurdles sometimes.

The main one is getting that low mass slide to strip another round and get it into the chamber. That's why they have such stiff springs. The other one is the short runup...distance...to the magazine from the starting point after it hits the impact abutment.

I've had good success at getting the delinquents to run, but a few were real head-scratchers.

Whenever the OM subject comes up, I'm reminded of a poem that I heard years ago.

"There was a little girl who had a curl in the middle of her forehead. When she was good, she was very good...but when she was bad, she was horrid."

By the way, as a point of interest...In the 6-round magazines with the flat, dimpled followers...the springs and followers are identical and interchangeable with the standard 7-round magazines with the flat dimpled followers. The Wolff 11-pound/7-round spring can be used. More than any other variant, enough magazine spring is critical. The Wolff spring in the magazine cures a lot of OM ills.

 

[Fred_G]

Ordered a EGW series 80 firing pin stop. Bout $20 shipped. Will see how it does.

 

[cauldron]

"Black Army"

I had to look it up, and it looks like Colt started making the 'black Army' pistols in the middle of 1918.

So if the change to the radius was in January of 1918, there would be a few 'black Army' pistols with the small radius stop. (I think)

So now I won't feel chagrined putting a small radius stop on my Colt 01918 reproduction!

 

[1911Tuner]

So if the change to the radius was in January of 1918, there would be a few 'black Army' pistols with the small radius stop.

Nope. They implemented the change about 6 months before the "Black Army Colt" appeared.

 

[cauldron]

Well... poop. Wikipedia failed me again.

 

[Greg528iT]

As a possible side effect.. As I stated before, my STI Spartan IV 9mm has a straight chamfer stop. It has a maybe 1/32" bottom surface. NOT enough to really put any radius on it. The edge looks to be just the machined edge, nothing horribly sharp.

When I re assemble the slide, the stop has always hit the disconnector and STOPPED, I'd have to apply more than normal force. A bit more than my other 1911s.
There is no radius to help cam the disconnector down. It's not a show stopper, but, if one decides to try a very small radius pin stop, a new hiccup might be in putting the slide on.. is probably the disconnector not wanting to cam down as easy. I just pushed the disconnector down with a screw driver so it was all just a smooth slide together motion.

 

[1911Tuner]

When I re assemble the slide, the stop has always hit the disconnector and STOPPED, I'd have to apply more than normal force.

Sounds like you need to hit the bottom of the firing pin stop with a smooth mill file and cut it flush with the center rail then establish a light bevel to act as a cam. Got a picture?

 

[NacsMXer]

1858, thanks for your post and sharing your experiences.

I have a Kimber as well and am interested in fitting one of these Wilson stops. Could you please explain in detail exactly how much fitting was involved?

i.e. did you have to make the overall thickness thinner by sanding the entire backside? did you have to sand the sides a good bit to fit the extractor? did you need to remove a lot of material or a little?

Thanks!

 

[MCMXI]

NacsMXer, I didn't have to remove any material. All I did was put a small radius on the bottom of the stop. It fits very well and the Ed Brown extractor I'm using has just the slightest bit of movement.

 

[NacsMXer]

Thanks 1858. I'm going to give one of these Wilson stops a try in my Grand Raptor II. I have always wanted to try the EGW oversized square bottom FPS, but have been leary of being able to correctly fit it to my slide.

This next question is for 1911Tuner, or anyone knowledgeable on the subject. I run a reduced 19lb Wolff mainspring in my GRII to complement my trigger job/Harrison Design internals. I am currently running a 1lb heavier Wolff 17lb recoil spring to compensate for the reduced mainspring. I shoot traditional 230gr full house ball.

If I install a flat bottom stop, should I go back to a standard 16lb recoil spring or keep everything the same?

Thanks and sorry, don't mean to hijack the thread.

 

[Greg528iT]

Sounds like you need to hit the bottom of the firing pin stop with a smooth mill file and cut it flush with the center rail then establish a light bevel to act as a cam. Got a picture?

I'll probably hit the edge a bit, but as you can see there is not a lot of room to make a bevel or radius very big. I'll probably get an EGW and start from nearer to scratch.





It's flush with the center rail.

It might be a thing of.. done cause they can. Short of assembling the slide it seems to be fine.

 

[harrygunner]

I have a flat bottom firing pin stop (FPS) in my 10mm 1911. 'tuner' is a pretty good physicist, so I'm throwing this out there for his consideration.

When I first heard of this, the effect of the shortened moment arm on the force against the slide was obvious. But then I got to thinking the grip housing mainspring is compressed the same amount no matter the shape of the FPS by time the hammer locks back. So the net change in kinetic energy of the slide would be the same.

Then, I realized the square cut on a 'firing pin stop' alters the shape of the curve of work the slide does as it pushes the hammer back, forcing the slide to transfer more energy into the mainspring at the beginning of the slide's motion.

The shape of the curve of force against the slide comes from some trigonometry, but that's unimportant. Here's a graph with simple lines to make the point.



The X axis is distance the slide moves from left to right, the Y axis is force on the slide from the hammer. The reduction of energy of the slide is the area under the curve.

The bottom curve representing a 1911 with a FPS, shows how the slide loses more energy earlier in its rearward movement.

About recoil springs in 1911s - As far as the operation of a 1911, I don't see the recoil spring and slide looked at as a "springed mass" being important except for returning the slide to battery.

I propose that one should keep the recoil spring on the low side, chosen for reliable operation. That's because at the end of its backward motion and subsequent forward movement, the slide interacts with another independent system with its own time scale, the magazine. The top round in the magazine is a "springed mass". Why not give the magazine the time it needs to present a round to the forward moving slide. A stronger recoil spring reduces the time frame for the magazine to do that.

And the recoil spring does nothing for "delaying opening the breech face". I don't believe that phrase has a meaning for a 1911. The barrel link makes that a function of the distance the slide has moved to the rear. And for any realistic bullet weight, the bullet has left the barrel long before the link pulls the barrel down. A faster bullet causes the slide to move faster, but the net effect is the slide moves the same distance as a slower moving bullet when it exits.