[1911Tuner]

In response to this thread:
http://www.thehighroad.org/showthread.php?t=198006
Post #22...I conducted an experiment that turned out to be a learning experience.

Initial experiment data deleted. Technically a non-no, though the intent was purely in the interest of science.

5-inch gun...Firing reloaded ammunition consisting of a 230-grain cast lead bullet and 5.1 grains of Alliant Red dot...MV 840 fps...produced a shortened slide cycle with a 16-pound recoil spring...which I expected. What I didn't expect was that the slide almost made it to full travel. There was a stovepipe failure to eject, and the slide didn't lock. If there hadn't been an extended ejector in the gun, I doubt if the case would have struck it at all...or at least not with sufficient force to break it loose from the extractor.

Curious, I...and wondering what it would take to produce full slide travel with this no-length barrel. The answer came with a used 14-pound Woolff recoil spring, cut to 28 coils. Ejection was weak, but complete...and the slide made it far enough to lock on empty.
Felt recoil was much like firing a fullsized pistol in 9mm caliber...
but the slide made it.

While the results don't completely lay waste to my theory that the short-barrelled 1911 variants often short stroke because of barrel length...they do make it less of a factor that I supposed. That only leaves the slide's reduced mass as at least an equal consideration
in maintaining the necesary momentum to make full travel.

So mjolnir, I must concede to the fact that the slide will recoil much more efficiciently without a barrel, but you'll have to concede that
it is a factor. We also must take into account that barrel to bullet clearance of only .022 inch per side would likely allow enough back-pressure to drive the slide, so my next phase is to cut the barrel off just forward of the chamber shoulder...press a ring onto the barrel...and use a tube of larger ID to further reduce this back-pressure. This will entail boring out a barrel bushing to accept the tube.

Stage three will consist of milling away enough material from a junk slide to approximate the weight/mass of an Officer's Model/Defender class slide...which will probably look like something on the order of the
Beretta 92 Series slides. That'll have to wait until I can arrange a mill, since mine is dead in the water.

Stay tuned, flame war fans! This one promises to be interesting.

[jungle]

Interesting. My take is that by boring out the barrel you have reduced the velocity and therefore the momentum by the difference in 840FPS and whatever speed it is chucking them out at now. Any way to chrono the new freebored Tuner special barrel against a standard barrel with the same ammo?
The lower velocity would actually produce longer dwell time, not shorter in the same length of barrel.

[1911Tuner]

Howdy Jungle...Glad to see in on this one.

I'll probably chronograph it at some point. I'll take a WAG at the velocity based on the 40 fps rule of thumb and put it at about 640 fps, and...going by the felt recoil...even that may be a little high.

Also interesting is that the recoil spring that finally allowed full cycle was a near-ringer for the "Softball" spring that Colt includes with their Gold Cups.
I think that the reduction in slide mass is gonna be an eye opener. I'll predict that it will have at least as much of an effect as the barrel mod.

If this bears out...it would be that the short-cycle issues that plague some of the chopped pistols comes equally from both. it may take a while to arrange the mill and a junk slide. The only bad slides that I have are broken in two pieces...so I'll start shoppin'.

[Ditchtiger]

are you hand firing your project or using a machine rest?

[Jim K]

Well, residual backpressure probably has some effect on the slide motion after unlocking, but it has nothing to do with starting the action movement in the first place, which is solely due to recoil when the bullet moves forward. If the bullet doesn't move, the barrel doesn't move, and the slide doesn't move. The gun stays locked.

Now the tricky question is that given the operation is due to recoil, should bullet contact with the barrel be necessary at all? If we had a muzzle loading cannon, aimed it straight up, set a larger caliber ball on top of the muzzle, and fired it, the gun should still recoil, even though there is no barrel at all, and no confinement of the cannonball.

I love those experiments; it is part of learning and also makes for a lot of ideas (and controversy) on the site.

Jim

[sm]

:)

Great Thread! Thanks for all the time, efforts and donation of parts.

Awaiting results!

I have a question - going to wait as I think it may be answered after slide weight is reduced. :)

Steve

[1911Tuner]

Ditchtiger...I'm hand-firing the pistol.

.

Jim...One point. The barrel doesn't move backward until the slide moves...and pulls it backward. It remains locked as long as the bullet is present. Once the bullet exits, it's no longer truly locked. Think about how a 1911's lugs bear against one another. Barrel front lug wall to slide rear lug wall. Evidence is the flanging seen on badly worn or slap-seated barrel lugs.
It's always at the front...and the damage to the slide's lugs is always at the rear.

Think of it this way...Hypothetical firing of a round in a barrel that's freeestanding vertically on a breechblock with nothing tying the block and barrel together. When the bullet hits the rifling...is the barrel going to be forced backward against the block...or is it going to be pulled skyward with the bullet?

Your experiment resulted in a condition of forced equilibrium. Barrel being held forward under pressure, with equal pressure driving the slide rearward.
Bullet blocked by the rod/screw...which was mechanically locked to the barrel. Barrel locked to the slide, with nothing able to move resulted in nothing moving because the equilibrium couldn't be broken. Lock your hands in front of you and pull equally in opposite directions...Equilibrium.

Steve...You may have a lengthy wait, since I don't have a slide that I'm willing to hack up. I also have to travel quite a distance to have access to a good mill...about an hour and 15-20 minutes...all the way from Lexington to Danbury, NC. New rules at Forsyth Tech have put an end to my using the machinery there unless I'm signed up. Had a sweet deal over there with my bud, the Dean of Machine for several years...but it ended last fall with a new administration.

[1911Tuner]

Planned on heading for the range with some different loadings today. Slow, heavy bullet...Light, fast bullets...various springs, etc. bu rain has forced me to sit today out.

Pondering on this, it seems that the chamber may be the key that can't be altered for fear of case rupture...at least holding it in my hand for the testing.
I'll try to rig up a jackass machine rest and open the chamber up a little to see what effect that has. Best guess is that...as the pressures are allowed to expand outward as well as forward/backward...impulse momentum will fall.
I may wait until I can arrange for a slide to be butchered. Best guess on that is that a lightened slide will move sharply until the spring rate is increased accordingly...as with the sub 4-inch guns...and there will come a point that, when the alterations combine to make just the right conditions, (or just the wrong ones) I'll experience the same short-cycle malfunctions common to many of the little blasters.

I did learn something though...I was a little wide of the mark in my assumption
that barrel length was the main factor in the short-cycles. A factor, but not as much of one as I had assumed.

Maybe tomorrow will be a better day.

[jungle]

Tuner, I think the chopped versions of the 1911s suffer reliability problems for two reasons.

1. With a lighter slide mass they rely on a stronger spring to control slide velocity. This stronger spring is contained in a smaller area and tends to suffer as a result. Springs vary and most of the makers recommend more frequent replacement in the chopped versions.

2. The barrel in a chopped pistol has to move through a larger angle in relation to the bushing end of the slide in a shorter distance to achieve the same unlock range of movement. That is why the lower lugs are different on a Commander and shorter pistols. It is also why the General Officers version had different locking lugs.

[1911Tuner]

Jungle say:

>With a lighter slide mass they rely on a stronger spring to control slide velocity. This stronger spring is contained in a smaller area and tends to suffer as a result. Springs vary and most of the makers recommend more frequent replacement in the chopped versions.<
***************

Understood, acknowledged, and agreed.
****************************

And:

>The barrel in a chopped pistol has to move through a larger angle in relation to the bushing end of the slide in a shorter distance to achieve the same unlock range of movement. That is why the lower lugs are different on a Commander and shorter pistols. It is also why the General Officers version had different locking lugs.<

Also understood and agreed...but this doesn't explain the oft-noted failures to
fully cycle rearward. Most of the function issues with these guns are related to short-cycle problems...Either in stovepipe failures to eject...weak/erratic ejection...or bolt-over-base failures to feed. Lighter recoil springs usually help, but sometimes produce failure to return to battery until the barrel ramp/throat area is adjusted. The lighter springs combined with the reduced slide are the players here...with the mass probably being the most signifigant.

Which brings me to the question...Does the reduced slide mass also contribute to the short cycle issues via less efficient conservation of momentum?

I tell ya...Some of these little buggers have driven me almost over the edge tryin' to strike just the right balance...and when the time comes to change the recoil spring, it's back to square one. These problems go all the way back to the Detonics...so I've been cussin' at'em for a while now.

[Jim Watson]

Well, it seems to me and FLG that one reason the short 1911 mutants suffer from short recoil malfunctions is because their recoil stroke is shorter to begin with. Haul back the slide on an OACP or Commander and you will see that the breechface doesn't even clear the disconnector hole. The G.M. slide comes much farther back. That gives things TIME to happen that the nubbed off guns don't have as their short light slides travel a shorter distance faster. FLG has made up several of the old "bobcat" type guns with G.M. barrel and slide shortened to 4.25" but retaining the full slide travel for effective ejection and feeding.

I think the short gun's conservation of momentum may be TOO good. Elastic collision as the light fast slides bounce off the frame too fast for the magazine to bring up the next round. The reason that good magazine springs are even more important in a short gun than a standard one. My OACP gets Wolff extra strength all purpose magazine springs for a six shot capacity and very positive feeding.

[jungle]

Tuner, The factors that you and Mr. Watson have pointed out are the real crux of the problem.
Bolt over base failures=too high a forward slide speed for the magazine, short cycle/stove pipe=rapid reduction in slide's rearward speed combined with limited rearward travel and more rapid forward travel due to higher spring load.
The heavier slide in a full size pistol gives a constant higher momentum value and longer slide travel, when speed is controlled more by the springs and slide travel is shortened everything has to happen faster and the ballistic range for proper function is narrowed.

[Old Fuff]

Tuner:

You is all wet when it comes to this theory about the bullet having to engage the rifling to start unlocking the action. I know because blank cartridges can cycle the slide – even on Thompson’s. Don’t you ever go to the movies??? :evil: :evil: :D

To get more serious, in one of my more delusional moments I wondered what would happen if one of the little stinkers was set up with a free bored barrel, somewhat like a 9mm “NATO chamber.” By removing the rifling in front of the chamber I would expect unlocking would be delayed in terms of microseconds, and pressures would be lower.

Also, why don’t you try a couple of hardball rounds through your modified barrel and see if the slide still locks back? It could be that your lead bullet, even though hard cast, is upsetting enough to seal in the bore where a full-jacketed one wouldn’t. Ya’ might try a light slug (185 grains or so) and see what the results are too.

This is going to get fun… :)

[1911Tuner]

Jim...Big +1 on the Wolff springs in the short pistols...and agree 100% on the reduced travel/rebound point. All these things considered and allowed for/adjusted for...but still haven't produced consistent or repeatable results in the dozens that I've argued with over the years.

Jungle...you may have just hit on something that I hadn't thought about in depth...or at least not deep enough. Constant momentum rather than higher or lower momentum...or, another way...reduced slide mass being more sensitive to variations in ammunition. (Peak presures/acceleration rates/Muzzle Velocities.)

See if this sounds reasonable to you...

The heavier slide reacts slower to changes in acceleration...both backward and forward. Hence, ammo variation doesn't show as readily as it does with the short, light slides.

This much I do know: Slower, heavier bullets don't have the same issues as light, fast ones...even when the slow ammo is loaded to produce a similar reverse power factor. i.e. 250 grains/700 fps=175,000 PF and 200 grains at 900 fps for 180,000 PF. (Velocities calculated and adjusted for 5-inch barrels)

[1911Tuner]

FUFF! Sho 'nuff happy to see ya back on board! I was gonna write later today to see how things are goin'.

I thought about the lead bullet upset too...Might make some difference with a jacketed bullet, but with .022 inch clearance per side, it probably wouldn't make much. Maybe just enough to prevent lockback with some rounds, but...maybe not if another happened to be a little more lively. It would take
brass from the same lot...weighed...and weighing the bullets and hand-scaling the powder charges to keep things as consistent as possible.

Well...Since it's a rainy day in the Carolinas...I may go do that with a few rounds just to see.

[sm]

1911Tuner,
You know where I am going with the slide weight.;)

I understand hacking one up for <shudder> Experimenting. One would be left with a "cut-a-way" to see how the gun "operates". Educational tool if pistol "cut-a-way" leaving only what is needed to "operate".

Where I am going : Using a Standard 5" 1911. We have bone stock, we have those with attachments , and those attachments have optics. Folks have been known to have to change reloading to shoot with the added weight - when optics removed, gun runs, when optic mounts removed - gun runs as it did (more reliably ) bone stock. :) What and to what point would being "lighter" affect the balance JMB figured into this design?

Old Fuff,

Now don't go confusing folks, allow me , someone NOT near as smart as Tuner , Yourself, Kennan...et.al. [I'll never be anyway]

How come a Old Gov't model , shot so much there is only about one inch to maybe one and half inches of rifling left near muzzle, still 1) runs 2) combat accurate [4"] ?

Remove barrel from gun, look thru from chamber end, and see pretty much smooth, until that bit of rifling near muzzle?

Funny, another "Gubmint Barrel " just grabbed and stuck in the Gun ...worked from get-go.

That is why folks need to get rid of old stuff and buy new guns...

*grin*

[Jim Watson]

Fuff:
Movie prop guns if originally recoil operated like 1911, are normally converted to blowback to cycle with blanks. Often with a restricting orifice bushing in the barrel to hold back enough chamber pressure; as is routinely done with gas operated rifles to be shot with blanks.

[Old Fuff]

I know that !!!

Didn't ya' notice the :evil: :evil: :D at the end of my comment? I was just twisting Tuner's tail a bit. :neener:

Obviously if the modifications you mentioned weren't made the slide/breechblock wouldn't move. That stumped Hollywood for awhile. When Gary Cooper played Sgt. York they filmed the shooting with him using a Luger, rather then a .45 Colt, because they couldn't get the Colt to work reliably in rapid fire with blanks.

[mjolnir]

Wow Tuner, you're definitely not one to let the cotton grow under your feet!:)

I'm with jungle on the velocity loss. With enough clearance around the bullet, gas blow-by will be a problem as there is less energy imparted to the bullet and consequent lower velocity of the bullet. The important thing will be that the bullet exit the plane of the muzzle at the same velocity as from a normal barrel, otherwise the rearward impulse is proportionately lessened. I imagine a heavy crimp and upping the powder charge may help; however, PLEASE DON'T DO ANYTHING EVEN REMOTELY UNSAFE!! But you knew that.

I agree that barrel length is an issue in the sense that once the bullet exits the barrel, it's acceleration is over. The impulse the slide sees is related to the acceleration the bullet receives.

Shorter barrels, with powders that burn at the same rate, simply do not accelerate the bullet as much (which we see as the lower velocities from shorter barrels). This translates to a lower impulse to the slide, but with a chopped gun, the recoiling mass has decreased faster than the bullet's muzzle velocity dropped, resulting in increased slide velocity, and consequently higher needed spring rates, as slide/barrel length gets shorter. To boot, the slide now has to accomplish all its functions in a shorter stroke (and thus time span) because the recoil spring tunnel keeps getting closer to the frame.

It's like a well-oiled field goal kicking team. They've got their timing down perfectly, but now the holder is asked to set up 4' behind the center, the kicker one step away from the holder, and the holder can only set the ball in place for 1/4 sec. Yet the kicker must still kick the ball through the goalpost from the same distance away. That's asking a lot.

For a chopped 1911, I guess one thing to try would be to mill off the recoil spring tunnel of the slide to be only 1/8" thick (like a glock), in an effort to gain some more slide travel. You could even cut it off and weld it forward a 1/4" or so, so that it protrudes beyond the muzzle (which kind of defeats the purpose of having a short gun!).

So let's say powder technology advances, we can now accelerate a 230 gr. bullet to 830 fps out of a 3" barrel, with no increase in pressure. We now have the same momentum as generated from a 5" gun. Next, we increase the mass of the chopped slide by adding a tungsten sight rib (or however; and we won't worry about the mass of the barrel for this discussion), such that it's mass equals a 5" slide's. We still remain with the problem of slide travel length...and there's not much getting around that one with the chopped 1911 platform...perhaps some type of latching system that holds the slide rearward for a few milliseconds before releasing it forward...not very practical.

[Old Fuff]

sm:

How come a Old Gov't model , shot so much there is only about one inch to maybe one and half inches of rifling left near muzzle, still 1) runs 2) combat accurate [4"] ?

While the barrel may look shot out at the breech end there is usually some rifling left and/or the bore is tight enough (or rough enough) to grip the bullet so that at least unlocking will start.

One time some pistol smiths at an Air Force MTU took some shot-out barrels from issue pistols used for training, welded them up at fitted points, and used them to assemble match grade accurized pistols. Off of a machine rest they all shot into 4" or less at 50 yards. :what:

Apparently rifling isn't necessary for this kind of accuracy. :uhoh:

[1911Tuner]

sm axed:

>How come a Old Gov't model , shot so much there is only about one inch to maybe one and half inches of rifling left near muzzle, still 1) runs 2) combat accurate?<

Partly because the ones without rifling were still tight enough to effect a gas seal around the bullet. Note that my experimental barrel was opened up to .495 inch...and it cycled pretty well. Not optimum...but it surely surprised me. Most likely due to the fact that the fast powders reach peak pressure within an inch or so of bullet travel, imparting enough recoil impulse to get the slide moving...and once moving...conserved momentum carries it through.

Yep. I know where you're headed with the slide weight.:cool:

On the blank pistol/bore restriction/straight blowback thing...I saw a squib stick just far enough into the bore to completely cycle the slide on a pistol once...The empty cleared the port and the slide fed and went to battery on the next round...which caused the barrel to split from 3rd lug to muzzle at 3 and 9 O'Clock. The forward bullet nose measured about 1.25 inches from the
muzzle. Allowing for the one behind it pushing it forward, I'd guess that it probably moved just far enough into the bore to let the next one chamber...and the slide cycled. That means that enough momentum was imparted on the slide to keep it going, even though the bullet stopped.

[1911Tuner]

mjolnir said:

>We still remain with the problem of slide travel length...and there's not much getting around that one with the 1911 platform...perhaps some type of latching system that holds the slide rearward for a few milliseconds before releasing it forward...not very practical.<

Funny that you should mention that. I experimented with such a contraption once by form-turning a groove in the guide rod and using a rubber O-ring to delay the slide's return to battery...just at the right place for the rear of the
spring plug to climb onto the ring for about half its thickness...and it worked pretty well. Problem was that it didn't last long, and required changing the O-ring about every hundred rounds or so. Also made the gun feel like a pogo stick...but it did give the magazine time to catch up, and as a side benefit, it
cut down on muzzle flip from the slide smacking the frame, and noticeably so.

But...the problem with the short guns and mag timing can be neatly solved with standard Wolff 11-pound mag springs...and the issue lies mostly with short cycle...the slide NOT making it to the impact surface in the frame, or not making it with enough force to prevent a stovepipe failure to eject.

And:

>Wow Tuner, you're definitely not one to let the cotton grow under your feet.<

Hey! I'm retired and got time on my hands...in between dealin' with 12 dogs...I've got a lathe and I love to dink around with new ideas. Ain't no sense in sittin' around gatherin' moss when there's a challenge in the offing.

[sm]

Art's fault.
Make someone Think
Part of going to school is learning to ask good questions, knowing what resources to use, and how to access these resources, and best use. :)

Yep. I know where you're headed with the slide weight. :cool:
Figured you and others did :D

Remember Art's fault and all that other stuff...

So...JMB designed the 1911 with a 200 gr ctg. Gubmint and Them fellas that did testing "said" 230grainer.

Spring weights : Same or had to be changed?
Chamber/ Rifling : That seal was mentioned earlier...humm...any changes in chamber, throat, rifling to "better handle" the 230 grainer?

This Experiment - well already the fps have been mentioned with 230 grainers, and even these differed. Some folks use 200 gr, some 185 gr...have we ever had the question asked why a 1911 shoots one ctg better and not another? Anyone ever ask about the 165 grainers? *grin*

Yeah, that is also where I was going. I have not "gone" to Commander Size, and I personally have no interest in any 1911 platform smaller than Commander size because...

Exactly what this thread is dealing with. :)

The 1911 was "designed" with a lot more taken into consideration than many realize - especially today with so many clones, and the buying public "not" always aware of ...well...just 'cause it is new don't mean...well...you know? ;)

I have to go now, finals start tommorrow. I appreciate the mental break and I always appreciate learning from all of you.

Steve

[1911Tuner]

Fuff said:

>While the barrel may look shot out at the breech end there is usually some rifling left and/or the bore is tight enough (or rough enough) to grip the bullet so that at least unlocking will start.<
***************************

Apparently it doesn't need much. Looks like the amount of restriction just forward of the chamber shoulder...in the leade...is enough to at least drive the slide most of the way back. Maybe if I try a slower powder...Unique may
delay the peak long enough to show something.

Steve,

The original loading was a 200-grain bullet at 900 fps. Not a lot of difference in the recoil impulse there...and the initial transition was to a 234-grain bullet. The 230 became standard at some point after that, though I'm not sure when. The Old Fuff may have more exact information.

[Old Fuff]

Pat Yates is the acknowledged father of the little Detonics pistol. While studying to become an engineer he decided that a pocket sized .45 pistol would be neat, and made the first conceptional drawings during the mid-1960’s. In 2001 he wrote a long and detailed summary of his trials and tribulations with the Detonics.

Since he had little experience with the 1911 he followed Browning’s example of building a prototype, testing it and learning from it, and then building a new prototype and repeating the process. I have excerpted a small part of his 2001 paper below. I believe his observations fit will into this thread’s discussion, and invite other’s comments.

As for my own: I would offer that it was John Browning’s assignment to bring about a service pistol for the U. S. Armed Forces, and perhaps some others. Building a multi-purpose platform was not part of the picture. It is to the credit of Browning’s genius that his pistol has been adapted to so many different uses. However these are adaptations where the original design (including material specifications) is but a starting point. Adaptations necessarily involve some compromises, and compromises seldom offer optimal performance and reliability. The real test is consistent, repeatable, long-term reliability. In this area few, if any of the adaptations have matched the original’s record. Now for Pat’s report:

I photographed my prototype, one of the early production guns and an unmodified 1911 during the recoil/feed cycle at 3000 frames per second with the assistance of a retired photo technician from the Naval Warfare Center and a many-times-rebuilt surplus Fastex camera. What I learned was not too surprising.

Given the much shorter slide stroke of these guns and the lighter slide, the slide has a good bit higher velocity remaining when it slams into the frame compared to a full-sized 1911 or clone. With the stiffer recoil springing, it also has considerably higher velocity throughout its trip back into battery. This leads to two main consequences. First, when the magazine is full, the top round has trouble making it all the way up to full contact with the feed lips before the breech face of the slide impacts the case head. Fairly often, especially with ammunition heavier bullets, the top round will noticeably nose-down at this point. The impact of the breech face at the upper edge of the base of the round tends to drive the nose even further down as the point of impact is above the center of mass of the round, frequently causing it to jam into the magazine well just below the feed ramp. Lighter bullets seemed to avoid this and the case was usually in contact with the lips of the magazine when the round started forward. Bullet shapes with a smaller diameter meplat at the nose, like the H&G #68, were also more resistant to feeding problems here.

The other observation was that the round very often bounced from the slide face into the chamber well ahead of the breech face. This didn’t seem to be related to the feed failures during the limited testing that I could afford, but it did indicate the dynamics were a bit more frenzied then one would expect, and in fact with the few films made of the 1911, it was not observed at all there. At this point I no longer remember the actual slide velocity profiles of the three guns with the several loads tried, but do recall the prototype and an early production Detonics peak slide velocities were roughly half again those of the 1911 with the same loads. This cannot be accounted for by just the lighter slide mass if the impulse delivered to it is the same. The Detonics and the prototype’s slide just aren’t that much lighter. The smaller gun’s slide unlocked earlier, not much, but enough to increase slide velocity quite a bit. The 1911 slide was not only moving much slower when it impacted the frame, it rebounded forward to strip the fresh round much more slowly. This appeared to be important for two reasons. It allowed the magazine spring to always get the top round up against the feed lips, and it eliminated the frequent nose-down attitude of the top round with the heavier bullets. I built a Tungsten barrel sleeve to increase the recoiling mass prior to unlocking a bit, but by the time I’d got it done, it was pretty clear this was not an acceptable production solution, so I never tried it.

[jungle]

It would appear that springs are not nearly as effective as mass when it comes to controlling slide velocity, and the effect of mass reduction is out of proportion to the expected value.
The initial impulse applied to the breech face in a .45 ACP pistol is around 3,000lbs+, taken as the area of the base of the cartridge in square inches and multiplied by 20,000PSI. It is a short impulse at peak, but it's hard to see a spring resisting this at all in a normal configuration.

[Old Fuff]

In this Browning design the dwell time is determined by (1) the hole spacing in the link that pulls the barrel down out of engagement with the slide, and (2) the velocity of the slide. If all other things are equal, the dwell time will be most effected by slide velocity, and the faster the slide moves the sooner the barrel will be unlocked. So far everyone has looked at almost everything except the link. When a barrel is cammed out of engagement dwell time can be modified by changing the cam's shape, but Browning's link was designed to be used in one application, and in that application it works very well. Otherwise maybe not.

[jungle]

Quite true Old Fuff, if the barrel is riding the link. However if a properly fitted barrel is riding the lower lugs, the lugs will also limit linkdown geometry to some extent. It is rare to see a link in any modern tilting barrel design and I suspect the ability to control lock up and unlock with two different profiles on the two faces of the cam may be the reason why.

[1911Tuner]

Interesting observations. I have a suspicion that cartridge overall length and magazine release timing had more to do with his nose-down failures to feed than bullet weight. Colt evidently had (most of) the feed issues sorted out by the time they introduced their Officer's Models. For one thing...the recoil system was different. Many times, I've had nose-down issues with these pistols that have been solved by simply clipping a couple coils off the inner springs...which also helped greatly with the short cycle related failures to eject.


>It would appear that springs are not nearly as effective as mass when it comes to controlling slide velocity, and the effect of mass reduction is out of proportion to the expected value.<

Exactly so. I've always maintained that recoil spring rate has only negligible effect in delaying the slide's initial movement. The distance to unlock is just too short for the amount of compression over preload value to add anything signifigant. The mainspring...and the shape of the firing pin stop radius has the greater effect. Maybe if Pat had looked at the early design specs for the stop, it would have turned out differently for him. I've been using the early .078 radius...or even smaller...for a long time...making the stops from 4340 when I couldn't scrounge any at gun shows. John Moses really did know his business, it appears...

Jungle said:

> However if a properly fitted barrel is riding the lower lugs, the lugs will also limit linkdown geometry to some extent.<
*****************

Barrel linkdown and drop timing do have a telling effect on the overall function of the gun. In a few instances where the timing was good, but the barrel didn't drop quickly enough to get the desired drop clearance at the proscribed amount of slide travel, I've addressed it by modifying the shape of the forward radius on the lower lug, and opening up the top of the link hole to allow the lug to follow the slidestop pin. Opening the top area doesn't affect unlock and linkdown timing at all, so that issue can be adjusted to some extent, and it provides a fast barrel drop after disengagement...which is a good thing, since the best situation is to get the barrel the hell outta the way as fast as possible.

But...There's still the problem of short cycle issues in the chopped pistols. It can be addressed by reducing the recoil spring rate...but that brings on fast slide velocities rearward...which makes drop timing more critical...and it smacks the frame harder, which rebounds it harder, which makes magazine timing...Well...Ya'll get the picture.

Fine-tuning these guns is often a study in frustration, since they sometimes don't respond to standard tweaks...at least not consistently enough to standardize on technique. Jerry's "Officer's Model from Hell" was one prime example of my having to feel my way through. I got lucky on that one. I'd really like to give'em up for Lent...but they're more popular than ever, it seems..so I gotta feelin' that they'll be showin' up here more frequently.

I REALLY like 5-inch guns!

[np15cgg]

Tuner's doing an experiment! I'm no rocket scientist, but "watching" this is a bunch of fun and - sometimes - I even sorta understand what the bigdogs are talking about. Tuner et al., just one request: when all is said and done could you provide a synopsis for the plebes? A bunch of us are trying to learn just a bit of what you guys know, Thanks!

[1911Tuner]

Anybody know what synopsis means?

Dangit boy...Speak English!:D

[HankB]

Once the experiment is done, I remove the barrel from the slide...which takes me out of danger. The sawed-off shotgun barrel only becomes illegal when it's attached to a receiver. Once removed, it's just a steel tube.IANAL, but the BATmen might construe you to be in "constructive possession" of an NFA weapon, much as I would be if I had a 14" barrel for my Benelli shotgun, whether it was attached to the firearm or not. (Remember, these guys are capable of the mental gymnastics required to define a short length of shoelace as a machinegun. :rolleyes: )

If I were you I'd get rid of that short unrifled barrel ASAP before Agent Schmuckatelli comes calling.

(The results of your test were interesting, though! :cool: )

[Iggy]

This is a fascinating thread. I "think" I have learned a great deal about what happens when the ol gun goes bang.

I greatly appreciate the time you guys have taken to do the experimenting and discussing it here for the benefit of all of us..

A hearty tip of the Stetson to you all.

PS, Don't stop now!!!

Regards,
Iggy

[1911Tuner]

Hank...You may be spot on. I think I've pretty much found out that recoil impulse occurs sooner than I had figured...and though I'm not convinced that
a round glued to the breechface and fired with no barrel at all would drive the slide to full travel...I ain't about to set that one up.

Apparently the restriction afforded by the chamber is enough to build sufficient pressure to induce a goodly amount of recoil impulse...which means that I'm gonna have to rethink my stance on sub 4-inch barrels and ehir many quirks. Although everything means something...reduced bullet dwell time alone isn't the main culprit.

Well...back to the drawin' board.:rolleyes:

[1911Tuner]

I just had a thought. Instead of wastin' a perfectly good ruined barrel...why not turn a plug...shrink-fit it to the bore...and see if I can get a locked breech, recoil-operated blank gun to work...:scrutiny:

Don't touch that dial! Crankin' up the lathe later on today... :uhoh:

[np15cgg]

From the Greek, meaning an overview of something that is too doggone hard for me to figure out without bustin' some neurons.

Neurons: Greek again (!), meaning cells that I need a few more of to keep up with you all.

[1911Tuner]

Turned the plug, froze it, and heated the barrel. Pressed the plug in and it looked good...'til the two pieces started to equalize temperatures. The barrel split, from the muzzle to the face of the plug. No doubt the thin walls had a little somethin' to do with it...and I probably cut the plug a half thou too big.

Ah well...

[jungle]

Synopsis-Stick to the standard five inch barrel Government model or Commander.

[1911Tuner]

Jungle:

>Synopsis-Stick to the standard five inch barrel Government model or Commander.<
****************

Testify!

[sm]

...with USGI, Colt, or Metalform 7 rd mags.

fx= quality components designed to work as a whole quality firearm.

fx= Reliability.

[np15cgg]

In the mass of a Commander length slide and the 5 inch Gov'ment model? Are the differences in acceleration of the two distinct slide masses linear or higher order? Whatever the answer to this question, why do 6-inch slides - which, I guess, might exhibit an increase in mass that is proportional to the decrease associated with a 4-inch slide - appear to work just fine? If slow is not a problem, wouldn't all midget 1911 problems evaporate by reducing bullet mass (and therefore slide acceleration)?

Thanks in advance.

[1911Tuner]

Well...So far, reducing bullet mass and increasing velocity has appeard to have negative effects. The slide often doesn't make full travel rearward with the lightweight screamers, and behaves itself much better...though sometimes not...when bullet mass goes up, and velocity comes down.

Excedrin Headace #1911...:D

[sm]

Great thread that once again reminds and re-states:

Anytime something/ anything is introduced to or altered from original design, other factors will be affected as well.

Allergic to Aspirin - Pass the Tylenol Please.

I like the 5" 1911, I really really like the bone stock Gov't Model of 1911 with the aforementioned mags.

Steve

:)

[np15cgg]

To zero and you're (literally) shooting blanks. The only force applied to the slide is proportional to the mass of the gasses produced by igniting the powder and their acceleration. That mass will exactly equal the mass of the powder load.

If I understand this thread, shooting blanks in a 1911 doesn't apply sufficient force to the slide's mass to cycle the pistol, but the addition of even very light plastic bullets does - though barely. Again, even though the gasses from a blank cartridge must leave the barrel at the highest possible velocity, the reactive force applied to the slide is low.

Now if we increase the mass of an imaginary bullet from zero to 230 grain equivalents, the force applied to the slide must be determined by the increasing mass of the bullet and its decreasing acceleration by the (constant) force of expanded gasses.

I think, but the neuron count thing comes into play here, that the amount of work - roughly, force over time - produced by the ignited powder/accelerated bullet will become more significant as the time for which the gasses/bullet are retained in the barrel increases. Tuner, is that what you call "dwell time"?

[mjolnir]

oops...doubled up

[mjolnir]

In the mass of a Commander length slide and the 5 inch Gov'ment model? Are the differences in acceleration of the two distinct slide masses linear or higher order? Whatever the answer to this question, why do 6-inch slides - which, I guess, might exhibit an increase in mass that is proportional to the decrease associated with a 4-inch slide - appear to work just fine? If slow is not a problem, wouldn't all midget 1911 problems evaporate by reducing bullet mass (and therefore slide acceleration)?

6" guns have the same stroke...rear of recoil spring tunnel-to-frame, as 5" guns (more or less). The increased mass of the barrel and slide is somewhat compensated for by the higher velocity a bullet gets out of the longer barrel. That's to say, recoiling mass has increased, but there's more momentum available to the slide since the bullet's going faster. The problem is in reverse of chopped pistols: recoiling mass is increasing faster than bullet velocity is increasing, resulting in slower slide velocity (than a 5" gun).

Not really a problem, as long as the slide makes it all the way back. I mean, you could probably slow the slide down enough to see it shuffle with your eyes. Plenty of room at this end of the hall. A 1911 doesn't actually NEED to operate at [roughly] .05 seconds full cycle.

Reducing bullet mass (and slide acceleration) in dwarves solves nothing, since you're still working against the same recoil spring force, resulting in less slide travel...of which dwarves have none to spare...which is the root of the problem. Slow in a full-length stroke pistol is fine, terrible in a dwarf. Just ask Gimli.

As Tuner pointed out, you start to get into a vicious cycle if you try to reduce recoil spring force.

There's probably some optimum ratio of slide travel to cartridge length, and chopped pistols ain't got it.

* * * * *
Tuner, very ingenious with the o-ring...I think the spirit of JMB may at times haunt the cotton fields!

[waterhouse]

While I have nothing [intelligent] to add to the thread, I just wanted to say thanks to Tuner for the experiment and to the rest of you for the discussion. I've learned quite a bit, and hopefully after I reread it I will have learned a little more.

[JohnKSa]

I wonder if the results would be the same with a smoothbore that fits the bullet a bit better. Not anywhere near as tight as rifling, but a good match to the bullet diameter plus enough slop to prevent friction from being a big issue.

I can't help wondering if the jet effect from the gas escaping around the bullet is having an effect. Seems like that might be starting the rearward recoil earlier than might occur otherwise.

[jungle]

The effect of the gases can be approximated by multiplying the charge weight by 4700 fps in the momentum equation.
This is fairly insignificant in pistols, but in rifles with a 50 grn+ charge weight it can add quite a bit.

[JohnKSa]

I didn't mean to imply that it would have a large effect, just that it was having its effect during an interval where there would usually not be much going on in terms of recoil. Normally nothing moves until the bullet does. In this case, there is a significant amount of gas escaping around the bullet which is having some (perhaps not much, but some) effect.

[mjolnir]

JohnKSa, that's exactly the problem; considering that a typical .45 ACP charge only weighs roughly 5-10 grains, like you say, the effect won't be very big. The main effect is to reduce the acceleration of the bullet, since the gas is escaping around around the bullet's base once it's free of the case. If bullet's final velocity at the muzzle is less than 830 fps, there's less momentum to operate the slide.

That can be solved with a teflon cap (or exterior-of-the-case sabot), whose interior profile matches the bullet's ogive, and whose O.D. matches the plug's I.D. That'll take care of friction and gas blow-by. It's small mass can be compensated for by slightly reducing powder charge.

[np15cgg]

Thank you, mjolnir.

When you said, "There's probably some optimum ratio of slide travel to cartridge length, and chopped pistols ain't got it," I began to wonder if anyone had ever sequentially added or removed mass from a 1911-pattern slide to measure resulting changes in cycling/dwell time/slide velocity. Old Fuff's excerpt regarding the Detonics pistol suggests that somewhere, someone must have done this sort of thing in a thorough way. Does anyone know whether or not such data exist?

It also seems that whereas the engineering and intuition of Browning can not be over stated, contemporary computational tools might be able to model a 1911's behaviors pretty well and prove useful in design choices. Is there just not enough money in this area to justify the effort? Perhaps that is the synopsis.

[Old Fuff]

I could easily answer the core question by pointing out that sub-compact 1911 pistols don’t work for the same reason bumblebees can’t fly… :D

The problem is that bumblebees do indeed fly, and some sub-compacts do work. So the focus perhaps should be, “why some, but not others?”

One thing should be clear, there are (at least) two issues. One is getting the pistol to be reasonably reliable, and the other is how to keep it that way over the long run.

All automatic pistols comprise a mix of balances between moving parts, cartridge energy (which provides the “push” to make things happen), and spring tensions – which in the 1911 design include the main spring as well as the recoil and magazine springs. As the slide cycles certain things must happen at precise times. When they do things work. When they don’t then the pistol doesn’t.

When you add the cartridge’s overall length and bullet nose shape matters become even more complicated.

Pat Yates noted that his high-speed photographs of the stock 1911 pistol showed even performance, where those of his two Detonics pistols exhibited differences that had negative connotations. These included failure of the cartridge to position itself in the magazine before the breech face returned to hit the case rim, and the cartridge being booted forward ahead of the breech face and obviously not coming up under the extractor. The solution might seem to be, “slow things down a bit,” and the ideal perhaps is to reduce slide velocity to no more then that of the regular model. If so, then the next issue would be, “how is this best accomplished?”

Just to stir the pot a bit… :evil:

Colt used to make a .38 Gold Cup that used a modified straight-blowback action. In it the barrel acted as a short-stroke piston to impart enough “push” to the slide to cause it to cycle. Maybe it’s trying to tell us something about slide impulse… :scrutiny:

[1911Tuner]

Sorry group...been outta the loop for a couple days. Long story, but no time to tell it.

Old Fuff reveals:

>Pat Yates noted that his high-speed photographs of the stock 1911 pistol showed even performance, where those of his two Detonics pistols exhibited differences that had negative connotations.<
**********************

The very thing that I've had in mind. The fullsized guns aren't as sensitive to variations in ammo, while the shorties respond quickly and instantly to slight differences in bullet weight and pressure. If we look at the specs for hardball...830 +/-25 fps, we have an extreme spread of 50 fps and be within spec. Here, we have a potential for a 6% difference in recoil impulse...and there are still other variables to consider as well. Variations in recoil spring load rates from spring to spring. Mainsprings, too must be factored in. With any coil spring, the fewer number of turns, the greater the error if the wire varies. Primer force, case capacity, and bullet weight. EVERYthing is SOMEthing. Jacket material too...as jackets are thicker and offer more frictional resistance...or thinner...or softer...and offer less. Things that a 5-inch gun would take in stride, but things that the sawed-off tilt-barrels can't cope with.

Thoughts?

[ABBOBERG]

Is this thread about chopped-down 1911's or all chopped-down semi-autos using the Browning-petter style action?

[jungle]

ABBOBERG, It is about the Browning style. Petter did away with many of the problems.

Making the shorties think they are longer. 1. Increase slide travel by shortening the spring plug area at the front of the slide and lengthening the dust cover and spring tunnel length. Think Glock slide. This would allow for a more reasonable slide travel and more managable spring lengths and weights.
2. Impart greater mass with tungsten insert(s) in the slide. Alternately increase mass by making the slide slightly taller and/or thicker.3. Use a barrel design with a cam and locking on the ejection port ala SIG or Glock.
That isn't a 1911 you say? Yes, but it works.

[1911Tuner]

Jungle said:

That isn't a 1911 you say? Yes, but it works.
*************************

Well...Technically, they're not 1911s anyway, so it's probably a moot point.
Neither are Commanders 1911s. If ya wanna get into pure nitpick mode, neither are 1911-A1s...but I ain't quite that bad.:D

[jungle]

If you want a 1911, 1911A1 or Commander get one. The design works well.

If you want a smaller .45ACP think about a Glock 30. The design works well.

[1911Tuner]

Jungle...+1

[NineseveN]

So does this mean that I'm supposed to be having all sorts of problems with my 4" Lightweight SA Champion? Cuz if it does, I'm just not seeing it materialize out here in happy land...

Perhaps the bull barrel and the lack of a bushing changes things, but I'm not so sure this Champion (or any other for that matter) is a problem waiting to happen. Now the 3" guns, they never did seem to get those ones to work quite right; of course, I don't keep up on guns I don't own, so take that stab with a grain of salt.

[Old Fuff]

In general the problems seem to be the worst in guns with barrel lengths of 3 1/2" or less. Those such as the Colt Commander with a 4 1/4" barrel and bushing, or others with 4" barrels without a bushing are O.K. This would seem to indicate that for maximum reliability one shouldn't go below 4 inches. But there are exceptions, the Colt Defender apparently being one.

[45auto]

It might be a novel idea for 1911 manufacturers, so perhaps another pistol company could "design", i.e. not copy, a 1911 "type" pistol in 3.5" or shorter that actually works one model after another. It's not like there isn't a market for them and you don't have to sell them cheap either.

But, I'll answer my own question :) . Why spend any money on "design" if you can sell plenty at $700-$1,000 and they don't even have to work that well.

Call it the "Bumblebee". ;)

[NineseveN]

Good point 45auto.

[1911Tuner]

Lemme post a disclaimer lest anyone who does have a good Bumblebee take it personally...

These observations don't come with one or two or even a dozen guns. These Bastard Stepchildren have been around for something over 25 years now,
and I've seen a bunch of'em puke.

It's not to imply that NONE of the guns work. Many do, and work very well.

It's not to imply that yours doesn't. If you say that it does, I'm sure that it does. I've never won the lottery, but I'm personally aquainted with two people who have...so I know that stories of major bucks lottery winners are true.

The point is...and always has been...that you, me, and Joe Average...as individuals...are much less likely to buy any given sub 4-inch 1911 pattern pistol that will hit the ground runnin' and never stop than we are with any given 5-inch gun.

Another disclaimer:

This is not to imply that there aren't 5-inch guns that give problems...nor does it imply that there aren't 4.25-inch Commanders that give problems.

For the 437 thousandth time, the percentage of guns with barrel/slide dimensions less than 5 inches that give problems is far greater than those
WITH 5-inch slide/barrel dimensions...and the shorter it gets, the more likely that you...as an individual...are going to have a problem with any given gun.

AND...The shorter they are, the tougher the problems are to correct when they do occur. The answer to this seems to be that the window gets narrower as the slide length and mass drop.

[sm]

1911Tuner,

Agree.

For those wanting a 1911 style pistol in a short version - See Colt Mustang in .380. Gets into that payload to ratio bit.

Run_Shorty_Run :

J frame, Colt DS, Security Six, NAA Mini-Revolvers,.. etc.,yeah wheelguns.