1911 Squib Cycle

[Chuck Warner]

Uh...I'm a little confused. Explain exactly how gases that are traveling forward under pressure in front of the bullet aid in driving the slide backward? The last time I checked, in order to make an object move in a given direction, I had to apply force in that direction. Your claim is rather like saying that I can mow my yard by running away from my lawn mower.

I understand that gas exiting the barrel at high speed has mass and causes a certain jet effect...but the tiny amount of gas blowby would have virtually zero effect. A little like slapping a stock car as it passes on the backstretch at Talledega. You've added a little...but not enough to make any sort of practical difference on the outcome of the race. OR...conversely...having a fly sitting on the top of the slide when the gun fires. The fly's mass will have some effect on the slide's acceleration...but to what degree?

If we assume that the entire (typical 5-grain) gas plug exits the barrel behind the bullet at 2,000 fps...which I seriously doubt...the recoil impetus of 5 grains of gas at 2,000fps would be roughly equal to an eighth of that imposed by a standard-velocity .22 short.
(32 grains at 1,000fps)

Ok, then we'll go back a little.

Let's for the moment ignore the gas effect created when the bullet leaves the case and start immediately after the bullet obturates.
You now have the bullet, case, barrel and slide locked together. In reality they are already moving due to the event Log described.

But, using a spring piston analogy as you brought up and eliminating any gas effect, you now have pressure expanding,and moving the bullet down the barrel, consequently applying pressure to the air column in front of it. This transferrence of energy and pressure is exiting the barrel and pushing the whole assembly rearward, before the bullet exits.
Quite simple and evident.
You saying it has little effect is where your figuring goes wrong.
Lets say the slide assembly weighs 2 lbs. Spring pressure at 16 lbs. Atmospheric at 15 lbs.
That would mean the air pressure exiting the barrel only needs to overcome 34 lbs of resistance to start the slide assembly moving.
Wanna bet the air pressure in front of that moving bullet is significantly higher than that?
Regardless of how the bullet obtains its velocity in the barrel, the pressure cannot be negated. Thats where your theory goes wrong.
You not only asked the question but answered it as well.

The Lawnmower thing was...well....lost.

 

[log man]

Perhaps CW overstated the affect of vacating the air column effects on the slide, often an overstatement is the only way of expressing the influence. "You keep eating like that and you'll kill yourself." Another example of the column of air being pushed out is to hold an air hose and release a short burst, overstated perhaps, not the same, yes, but ponder. That column of air is resistant to the bullets venture out the tube and that resistance is visited on the barrel and slide. A 1911 will fire in a vacuum and will venture that the velocity at bullet exit will be higher in the vacuum, due to not having to push the air out. If you are pushing against something, it is pushing back.

The stock car would be able to attain higher speed if it weren't forcing it's way through the air's resistance. No?

LOG

 

[1911Tuner]

I see what the points are. I just disagree strongly with the notion that the gas blowby initiates the slide's movement...or that it even adds anything significant to its acceleration during the bullet's trip. Unless I'm reading it all wrong, that seems to be CW's theory.

Whatever it adds...and I know that everything means something...in this case, it would be so insignificant that it can be ignored. If there was zero gas escaping past the bullet, it wouldn't make a whit of difference in what the slide does.

If we're going to argue that it adds 1/100,000th of a foot-pound of energy...I'll agree...but that would be some pretty serious nit-pickin' and not worth the bandwidth.

 

[Chuck Warner]

I never stated the gas blowby initiates the slides movement.

"Whatever it adds...and I know that everything means something...in this case, it would be so insignificant that it can be ignored. If there was zero gas escaping past the bullet, it wouldn't make a whit of difference in what the slide does."

This is incorrect. The bullets velocity, before termination in the barrel,even without blowby, would determine pressure exiting the barrel. Obviously enough additional thrust to cycle a fresh round into the chamber.

This you pointed out very clearly with the spring driven theory.



The blowby is merely evidence of the thrust applied to the breech via the casehead. That is the initial thrust that starts the slide moving. Once the bullet obturates, the momentum is continued by the compression of that blowby and air column forward of the bullet, and exiting the barrel.

..while we have been breaking it down into seperate segments, it really is one fluid event given the time frame it happens in.

The whole impetus was to explain how a squib could be fired and another round loaded. Once the bullet obturates and stops, by your own definition, nothing would happen. My own point was that with enough pressure escaping the barrel forward of the bullet, it can, and explains how it does.
We have wholeheartedly agreed that it does happen.

 

[Kruzr]

The mass of the gas (kinda catchy) is insignificant compared to the mass of the moving bullet. Most of the momentum is from the moving projectile. The "bang" starts the motion and the bullet's momentum is conserved by moving the slide back. When the bullet starts moving from the bang, the slide starts moving.

As I see it, the "pregnant question" is how far does the bullet have to move down the barrel and at what velocity to enable the slide to cycle with a XX (pick a number) lb. recoil spring?

 

[Jenrick]

I'd say you could easily use a trigger pull gauge attached to the slide to determine how much force is needed to pull the slide back far enough to eject and chamber a round. Simply apply the same amount of force to a lead bullet (or any bullet for that matter) and see how far it goes into the bore. If it goes into the bore past the chamber now you know it's possible and how little energy is needed.

-Jenrick

 

[Jim K]

Why should it not? The 1911 is a RECOIL-operated* pistol. And recoil begins the instant the bullet begins to move, so if the bullet moves at all, recoil begins. Since enough slide momentum to operate the gun takes place before bullet exit, any squib load that is enough to move the bullet to the end, or just out of, the barrel will operate the gun and load another round.

With one bullet in the barrel, at or close to the muzzle, and another fired behind it, the result will be a bulged or burst barrel. If, in some way, the first bullet is back against the second, with no significant gap between them, the two bullets will act like one heavy bullet; the recoil will be excessive, but there will be no damage to the gun or barrel.

Jim

*"...the thrust applied to the breech via the casehead. That is the initial thrust that starts the slide moving." Nope. In a recoil-operated pistol, recoil starts the barrel-slide unit moving, not the pressure of the case head on the slide, which only tries to separate the barrel and slide. It can't do that because of the locking lugs.
Pressure on the breech face pushes back the slide on a blowback pistol, but not on a recoil-operated one.

JK

 

[Chuck Warner]

Yep. It does and was widely covered in this thread. If the cartridge doesn't cause recoil, what does?

Recoil is a result of cartridge ignition and the resultant chain of events.

 

[Chuck Warner]

That would be a good start, but you would also need to attain velocity to get a true measure. Thats where it would get tricky.

Good thinking though.

CW

 

[Jim K]

Recoil backward is the result of the bullet moving forward. Of course the bullet doesn't move without pressure, but it is interesting to note that if on, say, a bolt action rifle, the barrel is totally blocked so the bullet cannot move, there will be no recoil.* And if that is done to a M1911 type pistol, the slide will not move.**

Jim

*Hatcher did it with a Model 1903 Springfield.
** My own experiment, using a strain gauge between barrel and frame to prove the slide doesn't move.

JK

 

[Chuck Warner]

You clearly agree with whats stated then. No bullet movement, no exit pressure=no recoil.

Simple.

Glad we could agree on something without petty insults.

 

[Chuck Warner]

Double

 

[TonyT]

I was shooting steel plates with a freind who suddenly found that the slide on his 1911 would not open. He had a bulged barrel which apparently resulted from firing a round after a squibb/semi-squibb load. Luckily he was firing a 45ACP with mild lead bullet loads and the only issue was a barrel replacement.

 

[log man]

I was shooting steel plates with a freind who suddenly found that the slide on his 1911 would not open. He had a bulged barrel which apparently resulted from firing a round after a squibb/semi-squibb load. Luckily he was firing a 45ACP with mild lead bullet loads and the only issue was a barrel replacement.

Good example, all the prime ingredients. The key for me to grasp this anomaly is the pressure that is holding the barrel and slide in opposite directions drops to zero when the bullet stops and the momentum of the slide carries it through.

LOG

 

[rsrocket1]

I didn't know that you can have a squib/semi-squib shot and have the slide cycle completely. Are you sure the operator did not manually operate his slide thinking that it simply didn't cycle properly?

It would seem that there are too many paths for the blowback gas to escape instead of causing the gun to completely overcome the recoil spring force and cycle the next round.

 

[log man]

I didn't know that you can have a squib/semi-squib shot and have the slide cycle completely. Are you sure the operator did not manually operate his slide thinking that it simply didn't cycle properly?

It would seem that there are too many paths for the blowback gas to escape instead of causing the gun to completely overcome the recoil spring force and cycle the next round.

The slide isn't acted on by blow back gases so much as the momentum acquired during bullet travel in the barrel. As I'm sure you are aware the slide and barrel travel to the rear .100" and it is a fast .100" travel in which the momentum is imparted to the slide.

LOG

 

[RogersPrecision]

My take on it........maybe it could happen.
It would require a precise (or lucky) combination of details.

My understanding of the physics:

The force pushing the projo down the barrel
exerts equal influence on pushing the slide/barrel (cannon) to the rear.

When the projo stops moving in the barrel, no further force
is exerted on the slide/barrel (cannon).

When the projo exits the barrel, no further force is exerted
on the slide/barrel. (cannon).

Once the projo stops moving or exits the bore,
the slide continues it rearward path soley from the momentum
given it, in its first 1/8" of movement.

The greater the friction encountered in pushing the projo down bore,
the greater the force exerted on the slide/barrel (cannon).

 

[Jim K]

FWIW, I have deliberately created squib loads that would cause the bullet to stop just short of barrel exit, and I can do it just about every time. The slide cycles almost normally and loads the next round (a dummy - I am not into bulging good barrels).

I don't want to give a powder charge, but a little experimenting will find it.

Jim

 

[Walkalong]

So, in my test, I needed to have a charge that sent the bullet almost all of the way to the end of the barrel (between 1.5 and 2 Grs) to get my 1911 to cycle the slide and load another round by the logic put forth here. Problem is, charges that got the bullet out of the barrel (2.0, 2.5, and 3.0) did not cycle the slide either, leaving the fired brass in the gun.

I still don't see how a squib that stuck a bullet could cycle the gun.

 

[1911Tuner]

I don't want to give a powder charge, but a little experimenting will find it.

And it'll vary from one gun to the next. I've had better luck duplicating it with 200-grain lead bullets and Unique. Jacketed 230s will cause the slide to cycle, but they don't usually drive quite far enough into the barrel to let the next round chamber.

The slide doesn't have to make the full trip backward. All it has to do is uncover the magazine. If the gun is a smooth feeder, it'll chamber the next one...and if you're in the trigger pull mode, you may not realize that something was wrong. If you hear a light *pop-hissss* you might as well start shoppin' for a new barrel.

It also seems that the common denominators are ammo loaded on a progressive machine and action/speed shooting. Slow fire gives the shooter's brain time to process the bloop and they usually stop and look.

Walkalong...That's the kicker. If the bullet exits...even if it hits the ground 2 feet from the muzzle...the slide won't make a full cycle. Only if it sticks, and just about the mid-point seems to be the sweet spot.

By the way...Thanks for steppin' up, Jim. People were startin' to say I'm plumb looney tunes for tellin' about this little trick.

 

[Kruzr]

People were startin' to say I'm plumb looney tunes for tellin' about this little trick.

That wasn't the reason.





(j/k)

 

[1911Tuner]

** My own experiment, using a strain gauge between barrel and frame to prove the slide doesn't move.

Jim, your experiment/demo was flawed. By using a steel rod against the bullet, and a screw threaded into the muzzle...you locked the system up.

The bullet was pressing on the rod, which was pressing on the screw, which was threaded into the muzzle. The slide didn't move...not because the bullet couldn't move forward...but because the barrel couldn't move backward, and thus, neither could the slide.

In the attempt to demonstrate that Kuhnhausen's "Balanced Thrust/Force Vector" description was wrong, you actually created one.

 

[1911Tuner]

The slide isn't acted on by blow back gases...

Well, sure it is. Objects are accelerated by force. In this case, the force comes from the expanding gases...the only force that's available...the same ones that accelerate the bullet. Until the object is moving, it doesn't have momentum. It only has inertia...resistance to acceleration. Momentum is the product of mass and velocity. No motion...no momentum.

the slide and barrel travel to the rear .100" and it is a fast .100" travel in which the momentum is imparted to the slide.

The barrel moves backward because the slide is driven backward and grabs the barrel by the lugs and drags it backward with it.

Technically, even the straight blowback is recoil operated. Force forward is force backward. Or...if you prefer...gas pressure forward is gas pressure backward. The only real difference is that the breechblock and the barrel in the blowback aren't mechanically tied together. Aside from that...it's pretty much the same.

See the photo below of an early Norinco barrel with insufficient upper lug engagement. Note the the lugs are deformed on the front faces...because the slide was dragging the barrel backward against the bullet trying to drag it forward. This one only had about .020 inch of lug overlap. The damage was incurred within 200 rounds.

 

[log man]

So, in my test, I needed to have a charge that sent the bullet almost all of the way to the end of the barrel (between 1.5 and 2 Grs) to get my 1911 to cycle the slide and load another round by the logic put forth here. Problem is, charges that got the bullet out of the barrel (2.0, 2.5, and 3.0) did not cycle the slide either, leaving the fired brass in the gun.

I still don't see how a squib that stuck a bullet could cycle the gun.

I have to agree while a physical test failure does not rule out the possibility it does further raise the question.

Walkalong...That's the kicker. If the bullet exits...even if it hits the ground 2 feet from the muzzle...the slide won't make a full cycle. Only if it sticks, and just about the mid-point seems to be the sweet spot.

By the way...Thanks for steppin' up, Jim. People were startin' to say I'm plumb looney tunes for tellin' about this little trick.

So less power than is required to cause a bullet to not exit imparts more energy to the slide, and cycles it, than a charge that does exit the barrel, and doesn't cycle the slide.

Please explain, why less is more, and more is less.

FWIW, I have deliberately created squib loads that would cause the bullet to stop just short of barrel exit, and I can do it just about every time. The slide cycles almost normally and loads the next round (a dummy - I am not into bulging good barrels).

I don't want to give a powder charge, but a little experimenting will find it.

Jim

Because I suspect you can't. What would be any kind of violation to share this phenomenon that you have such a great handle on. And why haven't you shown a video since it is so easy for you to duplicate this?

LOG

 

[1911Tuner]

So less power than is required to cause a bullet to not exit imparts more energy to the slide, and cycles it, than a charge that does exit the barrel, and doesn't cycle the slide.

Please explain, why less is more, and more is less.

Simple. Because when the bullet stops in the barrel, it no longer exerts a forward drag ON the barrel...which means that it also stops resisting the slide sooner. If it's moving, it's moving slow...which means that it offers resistance for a much longer time period. If it keeps resisting during the barrel linkdown, it brings the slide to a stop.

Again...The slide only has to move about .200 inch and the barrel drops. Once the barrel drops, the location of the bullet is irrelevant. It can be stuck in the bore, or it can be a hundred yards downrange...or it can be in China. It's all the same to the slide.

Because I suspect you can't. What would be any kind of violation to share this phenomenon that you have such a great handle on.

Log...I don't wanna be a jerk...but if you resort to snark and condescension, I'll delete your remarks. If Jim says that he can duplicate the squib cycle, it's because he can. I've been aquainted with him for several years here, and I've never caught him in a lie. I've done it a couple times, and I won't share the data either...for reasons of liability. If you'd like to experiment, feel free...but you'll have to find it on your own. No two pistols will produce the same results with a given load/bullet combination anyway. Each one is a law unto itself.