Roles of Springs in Recoil and Feeding of the 1911 Government

[Joshua M. Smith]

Hello,

I wrote the below for a member of another board. It became longer and more in-depth than I'd originally intended and I'm posting it on several boards because I realized it might help others when it comes to gunsmithing their 1911 pistols. When I searched for a similar online reference, I couldn't find one so I wrote one.

I'm not a 1911 expert. There are true 1911 artisans out there, and I don't belong to that society. Some do consider me an expert in the Mosin-Nagant, but I do not. I only study and report findings. A gun is a gun, but each has their own nuances which must be learned through intensive study, and a bolt action rifle is not a 1911. When I say "a gun is a gun" I only mean that they have the same basic parts, which may be extremely different.

They have bolts or slides which feed the rounds and keep them chambered for firing.

They all have hammers and firing pins (even if these are combined into single-piece units called "strikers".)

They all have sears, and all have disconnectors after a fashion, even if the "disconnector" is a manual separation of the sear and hammer mating surfaces.

All have springs, which are used to store energy for operation. In a manual pistol or bolt action rifle, this may only be the mainspring which drives the hammer. In a semi-auto, you may have three or more springs which all work together.

Discounting the sear spring for now, in the 1911 pre-series 80, there are three basic springs which work in relationship during firing:

1. The mainspring, which drives the hammer and retards the slide;

2. The recoil return spring, which does act against recoil but is really made to return the slide after recoil;

and

3. The firing pin spring, which returns the firing pin after ignition and prevents inertial firing.

Let us for a moment consider only the mainspring. Imagine a 1911 with no return spring nor firing pin spring. Imagine a round chambered and full magazine loaded into this hypothetical pistol.

When you squeeze the trigger, these events happen:

1. The hammer drops, striking the firing pin.

2. The round discharges.

3. The slide and barrel assembly recoil as one piece, against the hammer.

- This is important. This is the mainspring's role in managing recoil. The time the mainspring, through the hammer, can keep the barrel and slide locked together is called dwell time. Generally speaking, the more dwell time, the better. Early unlocking can cause a host of problems, from firing pin wipe to blowback of gasses during early unlocking.

- Hypothetically, on a Government, the hammer and mainspring should provide all the control needed to retard unlocking of the slide/barrel assembly. This is theoretical and I wouldn't try it.

- The original 1911 had a square-bottom firing pin stop. Because the military carried their pistols in Condition 3, and because some folks found it difficult to rack the slide with the hammer down in Condition 3 to ready their pistols, the 1911a1 was introduced as having a radiused FPS as one of its features. This allowed easier racking of the slide with the hammer down, but also hurt the dwell time. This wasn't important in a mass-produced fighting pistol, but most civilians ask more from their weapons and those who know change the stock radiused FPS to a square-bottom pre-a1 stop for better dwell time.

- Take away from this that the primary recoil and barrel/slide lockup timing control is the mainspring, NOT the "recoil" (slide return) spring.

Now, let's take up where we left off: The 1911 has recoiled against the force of the mainspring. The slide and barrel have successfully separated and now the slide is setting open after the extractor and ejector have worked their magic to discard the fired case.

There is another round just begging to be fed if something would only move the slide forward to do it!

Enter the recoil return spring.

1. Upon ignition, the recoil spring begins compressing, storing energy released from the round.

- The greater the amount of energy stored, the more force the recoil return spring will exert against the force of recoil. This means that the heavier the recoil return spring, the greater the feel of the recoil imparted to your hand.

2. At full slide rearward travel, resistance meets inertia, and the slide pauses momentarily.

- This is extremely important. If the slide doesn't pause long enough, it can actually overrun the next round up in the magazine! This is also why weak magazine springs cause malfunctions. Shorter 1911 pattern pistols like the Officer's have less inertia in their slides, which make them more dependent upon springs for the same power ammo, and make them more sensitive to changes in their working environments and tolerances than the 5" version of the same model.

3. After the pause, resistance overcomes inertia. The energy stored in the recoil return spring moves the slide forward, stripping the next round from the magazine and loading it into the pistol's chamber.

All's well, right? Well, no. Remember inertia? Your firing pin is an inertial firing pin, meaning it cannot touch the round's primer and the hammer at the same time.

So, now that we have forward inertia, the inertial firing pin slams into the round's primer as soon as the slide and barrel lock and slam suddenly to a stop. Buuuuuuuurrrrrrrrrrrrrp! A firing pin in motion tends to stay in motion, and all that. The feds frown on runaway guns as fully auto.

Therefore, the firing pin must have a spring to arrest its forward inertia, as well. In addition, a strong firing pin spring keeps firing pin wipe from happening: The firing pin must not be in contact with the primer when the spent round is ejected.

So, upon firing a 1911, one squeeze of the trigger does this:

1. The hammer drops, hitting the firing pin.

2. The firing pin slams forward under inertia. Some of this energy is stored in the firing pin return spring to return the firing pin to rest after the job is done, so that the above listed problems don't manifest.

3. The round ignites, and recoil begins moving the slide and barrel assembly backwards. The recoil return spring begins storing energy from the ignited round.

4. The barrel and slide move backward together about 1/4", providing enough energy to overcome the inertia of the hammer and start it moving backward.

5. The barrel and slide unlock after a safe dwell time and the round is ejected.

6. The slide continues rearward, fully cocking the hammer.

7. The slide pauses momentarily at full rearward travel.

8. The slide begins forward under the stored power of the recoil return spring. Before the slide can get up much forward velocity, it is slowed again as it strips the next round from the magazine. This is very important.

9. Due to the engineered slowing of the slide, it comes forward to a soft stop.

- This is why it's OK to chamber a round from a magazine, but not to drop the slide on an empty chamber! A slide dropped on an empty chamber is not slowed and will batter the lugs and cause the sear to bounce. It strains the gun.

10. The pistol is now ready to fire again.

Hopefully you now understand why a radical departure from stock weight springs is not a good idea, generally speaking. Yes, some do this, but generally for gaming, where they're firing reduced loads and have matched the springs to those loads.

The reduction of the mainspring reduces the amount of dwell time. The mainspring is very important to recoil management in the pistol. Reducing its weight reduces the ability of the pistol to handle full-power loads.

Increasing the recoil return spring's weight allows the slide to slam forward faster and harder than designed. If you're using weak magazine springs, you may have problems feeding, though this isn't an issue on Government-sized pistols as much as it is on shorter, smaller models. If they ever start using aluminum slides, it will be a problem on Government-sized 1911s.

An increased recoil return spring will also make the slide return faster, potentially battering the lugs and possibly causing sear bounce, which damages the sear nose and could potentially fire the pistol if said pistol has iffy engagement of the hammer hooks to the sear nose, including but not limited to short hammer hooks or negative sear engagement.

Hopefully this has helped someone.

Regards,

Josh

 

[RX-79G]

Couldn't keep reading. Dwell comes from a combination of things, but slide and barrel mass is the biggest one. Glocks don't have mainsprings to slow the slide and only use a recoil spring 2-3 pounds heavier than similar guns with hammers.

I would say the rest appears to be fairly well covered here and other places.

 

[Acera]

Thanks for that write up Josh. Good information explained in a very concise manner.


.

 

[Drail]

That was a well written piece. Making a 1911 run is a question of balance.

 

[RX-79G]

7. The slide pauses momentarily at full rearward travel.

Noticed this. I don't believe this is correct. The slide rebounds off the frame when it bottoms out against the front of the frame bridge - where the rails start. I would not expect two pieces of steel to smack into each other and stick for any amount of time, and the recoil spring has not bottomed out.

 

[45_auto]

Noticed this. I don't believe this is correct. The slide rebounds off the frame when it bottoms out against the front of the frame bridge - where the rails start. I would not expect two pieces of steel to smack into each other and stick for any amount of time, and the recoil spring has not bottomed out.

If you make your time interval small enough, any impact can be seen to "stick" before an object starts moving in the opposite direction as the objects deform. The slide and frame actually deform momentarily upon impact. As long as this impact remains in the elastic range, the materials will return to their original shape. If the impact exceeds the yield strength of the material, it will not return to it's original shape. Thus frame peening and the popularity of slide buffers for some 1911's.

Any time an object's velocity vector changes direction by 180 degrees, at some point it's velocity must be zero. No way to go from negative to positive without crossing zero. This small amount of time when the slide velocity is zero, as the slide and frame are deformed then return to shape as the slide velocity vector changes direction, is what Joshua M. Smith is calling the "momentary pause".

For example, if we define the bullet movement direction (towards the muzzle) to be the positive direction on a 1911, then the slide is moving at about negative 25 feet/sec when it impacts the frame. At some point this negative velocity (towards the back) must go to zero, and the recoil spring must start accelerating the slide in the positive direction for the slide to move forward and close. Again, no way to go from negative to positive without crossing zero.

Many people consider something with a velocity of zero (no matter how small the time interval) to be "paused".

 

[Joshua M. Smith]

.45_auto,

I kept mashing the "like" button, but it's only letting me like your post once. That was a wonderful explanation.

Josh

 

[entropy]

Hopefully this has helped someone.


Yeah it brought back bad memories of AIT.....and Basic, with the M16A1. Explaining the evolution of the M16 to the Drill. They do not like to be corrected.......

Very well written. Sure you didn't plagiarize Peter G. Kokalis? It's in his style of technical writing, but with explanations of why things happen the way they do.

 

[RX-79G]

45_Auto,

That is certainly true, but the point needs to be made that the "pause" is no different than the pause of a super ball bouncing off the floor. It is pretty much the time it takes for the two steel parts to compress as much as steel parts can, then release their energy into each other again. Not a pause long enough for another mechanical process to jump in or for a pressure to drop, etc. It is just bouncing.

I got the impression the OP thinks that the pause is more like the one when a spring is briefly overloaded at full compression, but most self loading firearms do not use their recoil springs in that manner.

So, now that we have forward inertia, the inertial firing pin slams into the round's primer as soon as the slide and barrel lock and slam suddenly to a stop. Buuuuuuuurrrrrrrrrrrrrp! A firing pin in motion tends to stay in motion, and all that. The feds frown on runaway guns as fully auto.

This is inaccurate. Because of the controlled round feed, the rising case rim is going to push the firing pin out of the way as it slides up the breechface. It is almost impossible to get a slam fire with a Browning tilt barrel when loading from the magazine, regardless of the firing pin return spring. It's primary function is making the firing pin stick out far enough to contact hammer.

 

[RX-79G]

- The original 1911 had a square-bottom firing pin stop. Because the military carried their pistols in Condition 3, and because some folks found it difficult to rack the slide with the hammer down in Condition 3 to ready their pistols, the 1911a1 was introduced as having a radiused FPS as one of its features.

The 1911 was meant to be carried condition 2 for one handed horseback use, which is why it has an inertial firing pin system and one handed decocking grip safety in the first place. The square slide stop was radiused very early on in pre-productin testing - 23 years before the introduction of the 1911A1.

 

[Joshua M. Smith]

Hopefully this has helped someone.


Yeah it brought back bad memories of AIT.....and Basic, with the M16A1. Explaining the evolution of the M16 to the Drill. They do not like to be corrected.......

Very well written. Sure you didn't plagiarize Peter G. Kokalis? It's in his style of technical writing, but with explanations of why things happen the way they do.

I didn't; never heard of the feller. I was raised by an engineer father who taught me a lot; could be that.

I'll look into this Peter G. Kokalis. Sounds like someone I may like to read. What does he write? (I won't have time til later to look him up.) What of his do you recommend?

Regards,

Josh

 

[Joshua M. Smith]

45_Auto,

That is certainly true, but the point needs to be made that the "pause" is no different than the pause of a super ball bouncing off the flour. It is pretty much the time it takes for the two steel parts to compress as much as steel parts can, then release their energy into each other again. Not a pause long enough for another mechanical process to jump in or for a pressure to drop, etc. It is just bouncing.

I got the impression the OP thinks that the pause is more like the one when a spring is briefly overloaded at full compression, but most self loading firearms do not use their recoil springs in that manner.

Not at all. It slows, then it stops, then it speeds up in the opposite direction.

Found this:


Just a couple, few milliseconds, if that.

This is inaccurate. Because of the controlled round feed, the rising case rim is going to push the firing pin out of the way as it slides up the breechface. It is almost impossible to get a slam fire with a Browning tilt barrel when loading from the magazine, regardless of the firing pin return spring. It's primary function is making the firing pin stick out far enough to contact hammer.

Eh, maybe. Maybe not. I've seen it happen. The barrel and slide are in-line before forward momentum has stopped, and without a spring, it's possible with today's softer primers.

Josh

 

[RX-79G]

Eh, maybe. Maybe not. I've seen it happen. The barrel and slide are in-line before forward momentum has stopped, and without a spring, it's possible with today's softer primers.

Then you need to be very afraid of AR15s, Tokarevs and Makarovs with their springless firing pins.

 

[Joshua M. Smith]

Then you need to be very afraid of AR15s, Tokarevs and Makarovs with their springless firing pins.

Naw, I'd be afraid of the SKS, too, and those things slamfire much more than those other designs. In fact, it's fairly common if you don't use military primers in the SKS.

If it's designed without a firing pin spring, then it's safe for the ammo specified.

Josh

 

[RX-79G]

The inertial firing pin spring is there to make hammer down carry possible. Making it sound like it is part of the recoil system's function is just missing the point of the device.

The problem I have with the OP is that you have attempted to deconstruct the function of the 1911 incorrectly and have gotten several historical facts about the gun completely wrong. The recoil system on the 1911 is not based on the mainspring. It works as a combination of mass, recoil spring and mainspring. I don't know why you would want to suggest that any one of those pieces isn't an essential and irreplaceable part of the system.

There are some things you said that are spot-on, but they weren't really mysteries no one knew about. I'm not sure what your goal in writing was, but much of what you put out is quite inaccurate and INCREASES the confusion surrounding 1911 pistols and similar weapons. You've just repeated many of the same old misunderstandings about the gun, reinforcing them in people's minds. That's unfortunate.

 

[Joshua M. Smith]

The inertial firing pin spring is there to make hammer down carry possible. Making it sound like it is part of the recoil system's function is just missing the point of the device.

The sole function of the firing pin spring is to keep the FP away from the primer unless smacked hard enough by the hammer.

The problem I have with the OP is that you have attempted to deconstruct the function of the 1911 incorrectly and have gotten several historical facts about the gun completely wrong.

Such as? Changes made in the 1911 culminated in the 1911a1. How have I deconstructed the operation of the 1911 wrongly?

The recoil system on the 1911 is not based on the mainspring. It works as a combination of mass, recoil spring and mainspring. I don't know why you would want to suggest that any one of those pieces isn't an essential and irreplaceable part of the system.

No, it's not based on the mainspring. I'd argue that it's based more on the mainspring than on the return spring, but the return spring cannot be discounted either. I wrote this attempting to describe the balance.

There are some things you said that are spot-on, but they weren't really mysteries no one knew about. I'm not sure what your goal in writing was, but much of what you put out is quite inaccurate and INCREASES the confusion surrounding 1911 pistols and similar weapons.

Such as..?

You've just repeated many of the same old misunderstandings about the gun, reinforcing them in people's minds. That's unfortunate.

What have I repeated?

Josh

 

[MachIVshooter]

The inertial firing pin spring is there to make hammer down carry possible. Making it sound like it is part of the recoil system's function is just missing the point of the device.

The problem I have with the OP is that you have attempted to deconstruct the function of the 1911 incorrectly and have gotten several historical facts about the gun completely wrong. The recoil system on the 1911 is not based on the mainspring. It works as a combination of mass, recoil spring and mainspring. I don't know why you would want to suggest that any one of those pieces isn't an essential and irreplaceable part of the system.

There are some things you said that are spot-on, but they weren't really mysteries no one knew about. I'm not sure what your goal in writing was, but much of what you put out is quite inaccurate and INCREASES the confusion surrounding 1911 pistols and similar weapons. You've just repeated many of the same old misunderstandings about the gun, reinforcing them in people's minds. That's unfortunate.

Agreed 100%.

Take more issue with this than the rest of the OP:

Hypothetically, on a Government, the hammer and mainspring should provide all the control needed to retard unlocking of the slide/barrel assembly. This is theoretical and I wouldn't try it.

Negative. As stated, the mass of slide and barrel being accelerated with the same force as the bullet (Newton's 3rd law) is what keeps them locked up until the bullet leaves the bore. It's the same principle as blowback, except locked breech recoil operated systems allow more movement of bolt/slide before the breech opens, allowing for much lighter components than possible with simple blowback.

The recoil return spring, which does act against recoil but is really made to return the slide after recoil

Both functions are equally important. Is why it's called a recoil spring, not a bolt/slide return spring; it counter-acts the momentum of the slide or bolt, slowing it. Too heavy, you get short strokes. Too light, you get slides or bolts battering frames/receivers.

Making a 1911 autoloader run is a question of balance.

There ;-)

 

[RX-79G]

Errors after a quick glance:
1. The square pin stop was removed right from the beginning. The 1911A1 changes did not have anything to do with the pin stop.
2. The 1911 was meant to be carried Cond. 3. It was built to be carried Cond. 2, which is why it has an inertia firing pin in the first place.
3. The mainspring is doing something special and essential, even though we can see that changes like square firing pin stops or even guns of similar design but no hammer demonstrate that the mainspring/hammer component is just a small part of controlling recoil. It is a component of the system, and arguably the least important after mass and recoil spring. Dwell time, in particular, is virtually all from slide/barrel inertia, not the influence of springs.
4. No one shooting .45 ACP needs "better dwell time". Unlocking early has never been a problem for 1911s, and even the most vigorous 10mm loads still unlock well after chamber pressures have dropped.
5. All guns do not have sears OR disconnectors. DAO guns don't have sears or sear like devices, and Glocks don't disconnect, they connect.

I don't think you have the perspective or understanding of the subject matter to post a lecture about 1911 function on a long standing gun forum. There are lots of people on this site that have been posting the correct information about the 1911 and related guns for a long time, and you should read those posts.

 

[Joshua M. Smith]

Negative. As stated, the mass of slide and barrel being accelerated with the same force as the bullet (Newton's 3rd law) is what keeps them locked up until the bullet leaves the bore. It's the same principle as blowback, except locked breech recoil operated systems allow more movement of bolt/slide before the breech opens, allowing for much lighter components than possible with simple blowback.

I don't disagree with what you said. The mainspring does help control the time till unlocking, not in distance but time.

The idea is to regulate the time over distance.

Distance controls the unlocking, but the mainspring helps control the time to travel that distance. So does the mass of the hammer, for that matter. And the mass of the slide, and likely the mass of the barrel because the slide is being slowed by the recoil spring.

The slide initially sets the barrel in motion during recoil, but after a couple milliseconds the barrel catches up and overtakes the slide because the slide is being slowed by the mainspring and recoil spring.

At this time, force switches from the front of the barrel lugs to the rear of the recoil lugs, and remains there until it disengages. The transition time is not long enough for the barrel to drop out due to gravity, and this is why the link is needed.

Josh

 

[MachIVshooter]

I don't disagree with what you said. The mainspring does help control the time till unlocking, not in distance but time.

The idea is to regulate the time over distance.

Distance controls the unlocking, but the mainspring helps control the time to travel that distance. So does the mass of the hammer, for that matter. And the mass of the slide, and likely the mass of the barrel because the slide is being slowed by the recoil spring.

Since you're dealing with acceleration (distance/time squared) and simple velocity (distance/time), the two are inseparable.

As pointed out, guns with no hammer still function fine. The tiny mass of the hammer and resistance from the main spring have no real affect on slide assembly acceleration (nor does the recoil spring). If you removed them entirely and somehow managed to still set of a round, your lock time would not change appreciably.

.45 ACP generates about 3,500 lbs of bolt thrust. A hammer providing 5 or 10 pounds of resistance is nothing.

The slide initially sets the barrel in motion during recoil, but after a couple milliseconds the barrel catches up and overtakes the slide because the slide is being slowed by the mainspring and recoil spring.

At this time, force switches from the front of the barrel lugs to the rear of the recoil lugs, and remains there until it disengages.

Nope.

 

[Joshua M. Smith]

Since you're dealing with acceleration (distance/time squared) and simple velocity (distance/time), the two are inseparable.

As pointed out, guns with no hammer still function fine. The tiny mass of the hammer and resistance from the main spring have no real affect on slide assembly acceleration (nor does the recoil spring). If you removed them entirely and somehow managed to still set of a round, your lock time would not change appreciably.

.45 ACP generates about 3,500 lbs of bolt thrust. A hammer providing 5 or 10 pounds of resistance is nothing.



Nope.

How?

The slide is traveling at x speed. However, the recoil return spring is offering 14-16lbs of resistance to the slide.

So, the slide imparts speed x to the barrel, so that both are now moving at x.

However, the slide is slowed by two forces, the 23lb mainspring and the 16lb recoil spring. Of course this resistance is not linear with the mainspring resistance falling off with leverage and the recoil return spring stacking, but we'll say it's linear for the sake of discussion.

So, for ~1/10", the slide is accelerating, but losing velocity, say x-y where y is the total resistance. However, the barrel is still traveling at x (with a nod toward friction from the barrel bushing, if present).

The question, then, is this: Can barrel traveling at x overtake, in 1/10", overtake slide traveling at x-y?

I think it might, depending on the fit of the lugs to the recesses in the slide, with tightly fit lugs shifting sooner than sloppy lugs. Then again, 1/10" may not be far enough. It's a pretty long way, though, when we're talking about milliseconds.

Josh

 

[RX-79G]

How?

The slide is traveling at x speed. However, the recoil return spring is offering 14-16lbs of resistance to the slide.

So, the slide imparts speed x to the barrel, so that both are now moving at x.

However, the slide is slowed by two forces, the 23lb mainspring and the 16lb recoil spring. Of course this resistance is not linear with the mainspring resistance falling off with leverage and the recoil return spring stacking, but we'll say it's linear for the sake of discussion.

So, for ~1/10", the slide is accelerating, but losing velocity, say x-y where y is the total resistance. However, the barrel is still traveling at x (with a nod toward friction from the barrel bushing, if present).

The question, then, is this: Can barrel traveling at x overtake, in 1/10", overtake slide traveling at x-y?

I think it might, depending on the fit of the lugs to the recesses in the slide, with tightly fit lugs shifting sooner than sloppy lugs. Then again, 1/10" may not be far enough. It's a pretty long way, though, when we're talking about milliseconds.

Josh

This truly doen't make any sense. The barrel and slide are a unit, locked together. As they travel together in a decelerating path backwards, the strain from chamber pressure goes to near zero and the rear of the barrel is cammed down. The vector of the barrel is diverted from back to down and it comes to a stop smacking into the top of the frame bridge. At no point since it started unlocking has it or the slide been under any power - they have been coasting together, and are now coasting apart, like two people holding hands who drop the connection to walk around a tree. There is no differential in their velocity or forces acting on them until after they are no longer touching.

 

[MachIVshooter]

This truly doen't make any sense.

Agreed.

From the moment of ignition until they unlock, the slide is pulling the barrel by the lug(s). What little momentum the barrel has on it's own during firing is forward, not backward. It is the slide continuing to pull it after the bullet has exited that imparts rearward momentum to the barrel; at no time is the barrel acting to drive the slide rearward.

 

[LNK]

45_Auto,

That is certainly true, but the point needs to be made that the "pause" is no different than the pause of a super ball bouncing off the floor. It is pretty much the time it takes for the two steel parts to compress as much as steel parts can, then release their energy into each other again. Not a pause long enough for another mechanical process to jump in or for a pressure to drop, etc. It is just bouncing.

If the frame were stationary and the slide hit and bounced off, the dwell or stopped time would be very short, but the frame and the slide continue to travel together under recoil, and as long as the slide return(recoil) spring can not overcome the inertia, they are in fact together for a longer time.

 

[Joshua M. Smith]

This truly doen't make any sense.

1. The powder ignites. The breech is sealed by the case expanding in one end, and by the bullet in the other.

2. The barrel and slide are one at this point, held together by the bullet and case moving in opposite directions. Barrel is trying to move forward; slide moves backwards pulling barrel; lugs are locked by shear force.

- 2a. ?

3. Link is pulled, barrel tilts down, lugs unlock.

I'm interested in the "2?"

During this time, forces are resisting the slide's rearward movement. Not by any great extent.

A couple pounds might cause a couple milliseconds' delay in rearward movement.

The timing dictates that the barrel and slide cannot unlock fully from each other for... what is it, 1/4", right? This is absolute, unchangeable, can't be changed without shearing off the locking lugs. Ain't happenin'.

The time it takes to travel that distance is what I'm referring to when I refer to dwell time in battery. (NOT the dwell time at the rearward movement; that's something else.)

The reason I operate under this theory is that it's known that squib loads, with the bullet stopping in the barrel, have cycled the 1911. This is rare, and seems to fly in the face of physics, but it happens.

Something else must therefore be happening. Generally the guns in which this happens are lightly sprung gaming guns.

If this were only occurring in blowback pistols, in which the inertial mass of the slide was the only thing to be overcome to cycle, then it would be easy to explain.

In a 1911 or other locked breech, not so much. It shouldn't happen, but it does.

My theory revolves around the forces holding the vertical faces of the top lugs together being not so great with a squib load, and the barrel moving rearward kinda sorta slightly independent of the slide -- in that the lugs are sorta' floating in the recesses instead of making firm engagment.

It's a theory, but it does help describe what I believe to be happening.

Re-reading, I think I may have come across terribly, and hope I've rectified that to a point with this post.

Regards,

Josh