Action type and physics

[1911Tuner]

conservation of momentum is responsible for recoil, and

Nope. Conservation of momentum isn't responsible for recoil. Acceleration is responsible for recoil. Momentum isn't a force. Momentum is the result of mass times velocity.

Momentum doesn't make things move. Conservation of Momentum is what keeps them moving after they get moving. Objects don't move unless a force is applied. See Newton 1A.
"An object at rest tend to remain at rest unless a force compels it to move.

Again...There's only one compelling force available to set everything into motion. That would be the force that results from the pressure that is generated by the expanding gasses.

Ok, I guess you could consider it to be kind of like a piston inside of a piston.

How is the barrel a piston? I'm literally sittin' here shakin' my head in disbelief.

The barrel doesn't drive the slide backward. The slide pulls the barrel backward while the bullet is moving through it. The bullet's frictionally-induced forward drag on the barrel, and the slide moving in opposition is what locks the breech via the lugs. It's like locking your fingers in front of you and pulling in opposite directions.

It's been fun, but I gotta go to bed. 0400 comes early in North Cackalackey.

 

[1911Tuner]

Ah! You watched the video. Interesting, what?

Read the next few paragraphs carefully.

Going by the response that you deleted...and I'm not tryin' to bust your chops here...just tryin' to educate you a little.

I know that the barrel and slide move backwards together, that is why it's not possible for the gas pressure pushing on the breech face to be the force pushing the slide and barrel backwards.

Why do you feel like the gas pressure/force can't push the slide backward? Again...It's the only force in the system. There is no other force in the system. While the slide and barrel are connected, they're essentially one mass. Think of it as a variable mass breechblock that "loses weight" when the barrel is disconnected. Here, it operates no differently than a straight blowback...except while the bullet is present...it's frictional resistance in the barrel is acting as a delaying mechanism...resisting the barrel's rearward move, and thus the slide's.

The bullet is moving forward...which means that the barrel can move backward. Because the slide is being driven backward by the force created by gas pressure...and because the lugs mechanically connect it to the barrel...the barrel moves along with the slide.

Grasp a broomhandle in front of you in both hands. Pull hard in opposite directions. Just when you're exerting a good amount of force...loosen the grip on the handle with one hand just enough to let it slip. When the handle starts to slip through your hand...your hand starts to slip on the handle. Now you have an action and a reaction. Before the slip....you had equilibrium from the balanced forces.

The broomhandle is the bullet. The slipping hand is the barrel. The wrist on the slipping hand is the locking mechanism. The forearm is the slide.

No, it doesn't matter that the compelling force comes from the outside...pulling both objects instead of from the inside pushing them. The "bullet" and the "slide/barrel assembly" don't know where the force is coming from. They only know that a force is compelling them to move in their respective directions.

To recap:

Momentum isn't a force. Momentum doesn't cause things to move. Force causes things to move. Momentum keeps them moving. Refer to Newton 1B...to wit:

"An object in motion tends to remain in motion unless an outside force is imposed on that object."

Here, Newton was describing conservation of momentum.

Recoil isn't a force. Recoil is the result of a force applied, and the acceleration that it suffered because of that force. Recoil is acceleration. Recoil only occurs during acceleration. Once the accelerative force is removed, and further movement is accomplished via momentum.

Once the bullet exits the barrel, the force goes with it. Neither bullet nor slide is being compelled to accelerate. They continue to move because of the momentum that they conserved during their acceleration...while the system was active...and they are now compelled by outside forces that are trying to bring them to a stop.

 

[1911Tuner]

Finally:

In a locked breech pistol, the heavy piston is locked into place, so it cannot move relative to the cylinder

How can the piston be locked to the cylinder? If that was the case...bullet locked to the barrel...neither bullet nor barrel could move. If the barrel can't move, the slide can't move.

A savvy old pistolsmith up in Maryland conducted an experiment years ago in which he used a steel rod and a set screw threaded into the muzzle of a 1911 barrel. He designed the end of the rod to prevent bullet deformation...to insure that the bullet couldn't budge a fraction of an inch.

He fired the pistol...and nothing happened. The slide didn't move and the gun didn't burst. The pressure escaped around the breech with a slow hiss...but nothing moved. Here, the piston was locked to the cylinder. The cylinder couldn't move backward...and neither could the slide.

It was an attempt to disprove Kuhnhausen's balanced thrust/force vector theory...but in doing it the way he did...he actually created balanced forces. A system in which the compelling and resisting forces were equal.

 

[General Geoff]

This would all be really easy to explain with a clear plastic mockup of a 1911..

 

[eye5600]

I would like to know where you found that radiograph of the 1911 in recoil. That's interesting on multiple levels and worth using as a teaching point, both for 1911's and radiography.

I think that you couldn't take a picture like that today. The X-ray dose must be very high to go through the pistol.

 

[Vern Humphrey]

My experiments (albeit with a weighted slide, not a fixed slide) show there is no difference. I explain it like this: There are four variables:

V1 = muzzle velocity (including gas velocity)
M1 = mass of the ejecta (projectile and gas.)

V2 = velocity of the moving parts (and ultimately of the gun)
M2 = mass of the gun.

The independent variable in the equation is V1 and the dependent variable is V2. By changing V1, you can change V2. But it doesn't work the other way. You can't change V1 by changing M2 or V2. At least not within the margin of error of the Shooting Crony I used.

 

[deadin]

He fired the pistol...and nothing happened. The slide didn't move and the gun didn't burst. The pressure escaped around the breech with a slow hiss...but nothing moved. Here, the piston was locked to the cylinder. The cylinder couldn't move backward...and neither could the slide.

I'm glad to hear this. Now I don't have to worry about my gun blowing up due to a blocked barrel.

Actually there's a much simpler, but less dramatic, way to demonstrate this.
You need a locked breech pistol that has an exposed barrel. (P08, P-38, Broomhandle, etc. A M1911 won't do because the barrel is enclosed by the shroud). Clamp the barrel in a vise, run a rod down the barrel until it contacts the breechface and push, nothing will come unlocked. In fact, you can beat on the rod with a mallet and the result will be the same.

I think that what is confusing some is saying that it is the "gas" pushing against the breech that makes everything operate. Think of the gas as merely providing the force. (Gas is ambivalent and will take the path of least resistance.) However the force created by the gas expansion follows Newtons 3rd Law and sends the bullet one way and the locked together slide/barrel the other. They will continue to be locked together until some mechanical linkage causes them to unlock. Then the residual momentum (Newtons 1st Law) takes over and the slide continues until stopped by the frame abutment/spring/buffer.

 

[1911Tuner]

Think of the gas as merely providing the force.

That's the point I've been tryin' to make...but I ain't gettin' through for somed reason.

It's really no more than pneumatics and heat. As more air is pumped into the cylinder...pressure goes up...and at some point, somethin's gotta give. Either it will set the system in motion or blow it up.

 

[Acera]

This thread makes me appreciate the finer details that had to be understood and accounted for by J.M.Browning when he designed the thing.

Making a complex system managing the forces and timing in such a simple manner is genius.

(Of course that is kinda overstating the obvious.)

 

[1911Tuner]

Making a complex system managing the forces and timing in such a simple manner is genius.

And the fact that Browning was never formally trained in engineering makes it almost mystical.

 

[1911Tuner]

Well...Dang. That ended abruptly. And just when I was cocked and locked and ready to rock.

Since it took a sidestep for a couple pages...Let's review.

Kuhnhausen was wrong. The slide moves while the bullet is in the barrel.

Blowback and recoil operated pistols are both recoil operated. Force forward equals force backward.
The same force that dirves the bullet away from the breechblock also drives the breechblock away from the bullet.

No rocket science necessary. It's no more complicated than Newton's 3rd Law of action and reaction.

Recoil isn't a force. Recoil is the result of acceleration due to force applied, and once that force is removed...all further movement is on momentum. Newton 1B. "Objects in motion tend to remain in motion."

Momentum isn't a force. Momentum is a function of mass times velocity. An object doesn't have momentum until it's moving...and force is what moves things...not momentum. Momentum keeps things moving after they get started.

The only force available in an internal ballistic event comes from pressure that comes from expanding gasses contained within the cylinder...the barrel...that drives the bullet forward and the breechblock backward at the same time. (You can't push on an object without immediately being pushed, and the size of the force when pushing is returned to you in equal measure.)

In a locked-breech pistol...The slide pulls the barrel backward instead of the barrel pushing the slide. The barrel doesn't recoil. It's just along for the ride.

The bullet is the main delaying factor in a locked-breech pistol due to frictionally-induced forward drag on the barrel. This is the one that so many overlook. Whatever frictional resistance is offered to the bullet by the barrel...is offered in equal measure to the barrel by the bullet. Because the barrel is resisted by the bullet's influence...and because the slide pulls the barrel backward...the bullet is likewise resisting the slide. Newton 3 works in both directions...whether pushing or pulling. (You can't pull on an object without being pulled by that object.)

John Browning was a slam-dunk genius.

Cheers!

 

[deadin]

Pretty good synopsis, but I'm not sure if I totally agree with your statement

The bullet is the main delaying factor in a locked-breech pistol due to frictionally-induced forward drag on the barrel.

There are several factors that delay the unlocking, with the forward drag being just one of them. Others are time in barrel, weight of moving parts that have to react to force applied, strength of recoil spring, weight of the bullet. Even the weight of the gasses produced by the burning propellant charge and their expansion rate will have an effect.
I'm not convinced that bullet friction is the main delay factor.

 

[1911Tuner]

Pretty good synopsis, but I'm not sure if I totally agree with your statement

I understand what is involved in the delay, dead...but the bullet outweighs all others combined.

Wanna prove it to yourself? Eliminate the bullet.

Load a blank with 10 grains of Bullseye, and put a tuft of cotton over the charge to hold the powder in the case. Work the blank into the gun and fire it. You'll be surprised at how far the slide will move with so little pressure and low mass on the other end.

Be sure and report back.

 

[deadin]

Bullet weight, yes, I agree that it is the main factor affecting lock time.
I was disagreeing with your statement of bullet friction pulling the barrel forward was the main factor.

The bullet is the main delaying factor in a locked-breech pistol due to frictionally-induced forward drag on the barrel.

Maybe your wording of the sentence wasn't what you intended to say.

 

[1911Tuner]

I was disagreeing with your statement of bullet friction pulling the barrel forward was the main factor. Maybe your wording of the sentence wasn't what you intended to say

My wording conveyed exactly what I meant to say.

Go push a bullet through a barrel...chamber to muzzle...by hand. The coefficient of friction doesn't lessen because the bullet is moving fast. Neither does it lessen because the bullet's momentum helps it along the way. It is what it is.

Whatever frictional resistance that the barrel offers to the bullet...the bullet offers to the barrel. The bullet moves through the barrel in one direction, and the barrel is pulled over the bullet by the slide in the opposite direction.

Think on it. Go load up the blank to see how little force is needed to move the slide without the bullet. Then, think on it a little more.

 

[deadin]

Then why won't my M1911 cycle with snake shot, leave alone blanks?

 

[1911Tuner]

Dunno. Maybe the shot cup to barrel friction is delaying it enough to offset the force/mass/momentum thing.

Try the blank. 10 grains. I've only been as far as 7 grains...and the slide moved far enough to put the hammer on half-cock. Standard half cock and not a Series 80 quarter cock shelf. 10 grains may get it all the way.

Try this..or at least visualize it:

Grasp a broomhandle in both hands at shoulder height in front of your chest. Pull in opposite directions. Loosen the grip of one hand juuuust enough to let the handle slip.

When the handle starts to slip through your hand, your hand starts to slip off the handle. As long as you maintain a grip, there is friction between the two. i.e. Whatever friction that your hand imposes on the handle, the handle imposes on your hand.

Keep pulling and keep the system moving. As your hands move father apart, you'll notice that the hand's movement is resisted by the handle...and the handle's movement is resisted by the hand.

The broomhandle represents the bullet. The slipping hand represents the barrel. The forearm attached to the slipping hand represents the slide. See it yet?

 

[deadin]

I fully understand your analogy with the broomhandle and I agree that a blank will provide enough force to unlock the slide and barrel, but there is not enough force to cycle the action. To obtain enough force there has to be enough mass to provide something for the expanding gasses to build up force. A blank, and in my case shot just doesn't have enough to do this. Especially with a blank where there is negligible barrel friction, if any.
Your example is to take away mass but keep the friction to provide something for the pressure to work against. This will work only if there is enough friction. I contend that if you take away friction and leave mass, the action will continue to cycle, albeit probably too violently for the design of the gun. As to which is the primary factor in operation, I will go with mass over friction. What the balancing point between more friction, less mass vs. more mass, less friction, I don't know. It would be interesting to do some empirical testing.
In both examples, if you take them to the extreme, i.e. sufficient friction or mass to allow the pressures to build beyond the strength of the gun, you will end up with a burst chamber. If the chamber and lock are strong enough to contain the generated pressure, nothing will happen. Presuming a perfect seal, how long the pressure would remain would be an interesting experiment.
I have to assume that it would remain until someone opened the chamber.

 

[1911Tuner]

Dead...Yer still missin' the point. Without the bullet, the slide and barrel don't lock.
The barrel lugs engage vertically, but they lock horizontally...under pressure and friction.
Lock your hands in front of you and pull. Like that.

About 2 years ago, I was watching a lady shoot the falling plate machine while I talked to her husband. I was looking straight at the gun when I heard a muffled pop. I saw the slide cycle...saw the empty case eject...watched the slide go back to battery.

Before I could stop her, she fired another round...and the gun locked up solid. It barely made a sound.

Two bullets nost to butt an inch from the muzzle with a big dog knot jammed into the bushing. Barrel split from third lug to muzzle at 9 and 3.

A squib cycled the slide far enough to chamber another round.


You can move it by hand with relatively little effort. Right?

Even as fast as you can rack it, it doesn't take garguantuan strength. Why? No bullet.

Try the 10-grain Bullseye/cotton blank. You might be shocked at how little force it takes to move the slide without the bullet's presence.

 

[1911Tuner]

if you take them to the extreme, i.e. sufficient friction or mass to allow the pressures to build beyond the strength of the gun, you will end up with a burst chamber.

The demonstration that I described with the steel rod blocking any bullet movement in the 1911 was performed by our own Jim Keenan...but it wasn't entirely his idea. Several years before, it was done by...if memory serves me...Charles Askins. The difference being that he did it with a 1903 Springfield rifle...and nothing happened.

 

[1911Tuner]

Awwww! C'mon dead. It'll take all of 5 minutes and a nickel's worth of components.

 

[deadin]

OK, I did it. It pushed the slide back far enough to partially extract but not eject the case. All it shows me is there was enough mass in the cotton and expanding gas to create enough force to partially operate the gun.
I would imagine that you could get a better result using an oversized wooden bullet. (More friction while minimizing the mass.) Of course I can maximize mass and minimize friction by using a smoothbore with a slightly undersized bullet.

Both ways will work, but what does it prove? You can no more eliminate mass than I can eliminate friction.
Sounds like we are arguing about how many angels can dance on the head of a pin.

 

[1911Tuner]

Both ways will work, but what does it prove?

Well...it provces a couple things. One is that the locked breech/recoil operated pistol works just like a straight blowback when the bullet doesn't influence the slide delay, and it proves that the slide doesn't require a helluva lotta force to cycle it without the bullet's influence.

Now, go load up a live round using a 185-grain bullet and about 3 grains of Unique. The pressure is much higher than with the blank...and the mass is much greater...but you may find that the slide moves about the same distance.

I'll say it again. The bullet is the greatest delaying factor in the locked breech pistol...and if you can't see it...it's because you refuse to see it.

But, I'll try again...just for the sake of greater understanding.

Hypothetically, of course.

Loaded cartridge...Drill a hole in the bullet and thread in a cable that won't pull through the bullet core. (This is unobtanium alloy that makes up the core.)

Load the cartridge in the gun and put it into battery.

Attach the cable to a steel block that weighs about a ton. Lock the frame of the gun in a vise that's bolted to a table that weighs about a ton. (We don't want any slippage that would give a false result.)

Pull on the slide until it moves backward. Yes. It can be done if you can exert enough force to move it.

You can even remove the recoil system and cock the hammer to eliminate any other delaying factor if you'd like.

You'll have to pull harder'n a billy goat can butt a stump to move that slide...against the resistance that the bullet offers to the barrel. I guar-on-tee.

 

[1911Tuner]

One last experiment, Dead...then I'll leave ya to your thoughts.

If you've got a .44 die set...size the case first in a .45 die. Then run it into the .44 die about a quarter-inch. Then...if you've got a .41 die set...neck it down to that size.
Now, try the 10 grain load and the cotton tuft. It'll probably lock the slide on an empty magazine. It may do it without necking down to .41 caliber.

What you do here is create a venturi effect. While it does raise the pressure a bit...pressure isn't the driving force. Mass times velocity is. Raise either one, and there is more force. More force forward equals more force backward. More force backward equals more slide travel.

Straight blowback...Recoil operated...All same-same. Both are recoil operated. The only difference is the mechanism used to delay the breech opening.

 

[deadin]

Well maybe if I go stand in the corner on one foot, hold my tongue just right and squint my eyes, I'll see it your way.

BTW It wasn't a Springfield that Askins experimented with. It was a Japanese Arisaka. He ended up running a 30/06 chambering ream into a 6.5 Jap loaded it with a case full of Bullseye and a .308 bullet. The barrel was set forward two threads, the case flowed back around the bolthead to the point that he broke the bolt handle off trying to open it, the stock shattered. but the receiver held. No blowup.
Supposedly he later rebarreld the action and continued to use it.