A Physics Primer

[RX-79G]

That recoil force *is* the gas pressure, acting on the area of the case head, in both designs. The 2 different names are an attempt to describe how the different mechanisms utilize and dissipate the energy created by the expanding gas.

Correct. All the different action names describe what is done with gas pressure, including a locked breech bolt action.

The question isn't whether gas pressure from combustion causes autoloaders to work. It does.

The question is whether gas pressure is directly harnessed to make them work. In the case of gas pistons and blowback, gas is used directly. In the case or recoil, the gas pressure has created acceleration of both barrel/slide and bullet. That recoiling movement is what unlocks and extracts the casing. Gas is no longer a factor at that point.

That's what 45auto and I have illustrated with examples of the forces involved, how recoil operation can be created without gas pressure and how recoil forces are unnecessary to make blowback go.

You can say they are all the same, but they are only the same in ways that have nothing to do with their individual definitions. Blowback and recoil are separate terms because they do, in fact, describe different uses of energy in a mechanical system. If they were the same, they'd have names that reflected that and would behave the same under our examples.

 

[RX-79G]

Youre talking like it is between the the bullet and barrel. It will be if you weld your breech with that TIG welder.
But now its open.

Nothing is open. They are locked together mechanically. Welding, bolting, pinning - it doesn't matter what method closes the breech - it's closed.

The slide, casing and barrel ARE the barrel until they are separated. They form a whole that is just as closed as a muzzle loader.

 

[Jlr2267]

{The barrel isn't dragged by the slide. They are one piece. It is a mistake to divide them into separate roles when they are clearly a unit. The only time the slide drags the barrel is when a hand pushes the slide back.}

The barrel is dragged in the sense that it moves rearward because of it's contact with the locking lugs, which are forced rearward...no locking lugs, no movement of the barrel...very simple.

{Yes, they will. As in my example, recoil alone accounts for more than enough energy to move a massive slide and barrel at significant speeds. I don't understand how M x V = momentum is up for debate.}

I'm sorry, but you are wrong. Momentum is not up for debate. Conservation of momentum is insured by *forces* acting equally, in opposite directions. There is no mysterious "momentum force." The force acting on the bullet accelerates it from zero velocity (momentum=0) to some muzzle velocity (where momentum=mass*muzzle velocity) down the barrel...an equal and opposite force (from the same gas presure) pushes the case/bolt rearward at some velocity that conserves momentum.

There are only 4 forces in nature, and one of them is *not* momentum. They are, in no particular order:

1. gravity
2. strong nuclear
3. weak nuclear
4. electromagnetic

The "recoil" force is electromagnetic in nature because it is the gas particles exerting pressure on the case/slide (and equally on the bullet). EM forces are what we experience every day when "touching" objects or pushing them around.

*All* forces we refer to with more common names, like "recoil," "centrifugal," etc., are in fact one or a combination of the 4 listed above.

If you think there is another force accelerating the slide rearward, you will need to explain exactly what force that is, and from where it originates.


{You have just stated that it does generate recoil. Now just consider what would happen if the barrel was not attached to the frame, but was only attached to the slide:

Recoil operation.}

Of course it would, due to electromagnetic force applied to the slide, not from some undiscovered "recoil" force.

 

[1911Tuner]

I never said ANYTHING about a plug FORWARD of the chamber.

Different board. Different argument. Let's try to stay in the present. RX mentioned plugging in front of the chamber and would like to use it to find that loophole that he's searching for.

But on your hypothetical plug at the back of the chamber...

If the plug is bearing against the slide...it'll recoil and drive the slide backward...probably full cycle. Otherwise, how is it that a bolt-action rifle recoils? By force backward against the bolt...or what?

All motion begins and ends with force.

Let's get back to balanced forces.

Here goes.

Firing with a solid plug in the barrel of a locked breech pistol,equal force is imposed forward and backward in the normal way.

But...

The plug is welded to the barrel. By default, whatever force that is imposed on the plug is likewise imposed on the barrel. Force forward.

Meanwhile, an equal force is imposed on the slide. Force backward.

Barrel and slide are mechanically connected...with equal force imposed in both directions...in opposition. One force is pushing backward on the slide, and the other is pushing forward on the barrel. Not on a bullet. On a plug that is welded to
the barrel.

This is known as balanced forces. The force resisting is equal to the force compelling...like standing in a bucket and trying to lift yourself off the ground by the handle. The harder you pull up on the handle, the harder you push yourself down.

Balanced forces don't produce motion. The result of balanced force is equilibrium.

Place all the force on the gun that you wish. Unless the lugs shear off, the slide won't move, because the barrel can't move backward.

If the barrel can't move backward, the slide can't move backward.

Do the same thing to an unlocked breech pistol, and the slide will move because the barrel and slide aren't connected. The force imposed on the plug and on the barrel doesn't have any effect on the slide. The slide is free to move from...wait for it...Force Backward. Recoil.

RX...as a happy coincidence, this also shoots holes in your other theory...the one about using a heavy bullet and high pressure to cause a locked breech pistol to unlock early.

A longer, heavier bullet imposes more frictional drag on the barrel...a resistance to backward movement, and whatever resistance is placed on the barrel is placed on the slide.

And more...

The longer the bullet stays in the barrel, the longer it imposes a resistance to the barrel's backward movement...and the longer it imposes a resistance to the barrel...it imposes it on the slide.

Because the slide is driven backward in recoil, and pulls the barrel backward with it.

And finally...

Trolling a member on a board that you moderate on

Yeah. Not real proud of that, but I wasn't a moderator then and I wasn't even into the gun boards all that much. I signed on here mainly out of boredom and made a few posts...and Handy jumped on me like a duck on a June Bug with a full measure of his typical snark. Don;t know why he singled me out, but there it was.

So, I was like...Okay. Let's do it.

I received a warning for it from Al Thompson and was asked to moderate a few months later. I've mended my ways.

 

[1911Tuner]

And now we've come full circle and back to the original points that got all this mishmash started.

Namely...whether locked breech, unlocked breech/blowback or delayed blowback...they all operate for the same reason by the same set of physics.

Newton 1. An object at rest will remain at rest, unless...

The slide is an object at rest that must be moved before the pistol can do anything else. The pistol can't operate until the slide moves. Yes? No?

When a round is fired in any of these, the same series of events takes place. i.e. The primer is struck, lighting the powder. The powder burns, and the gases expand. Pressure goes up and brings a forward and backward force to bear on the bullet and slide. The bullet is accelerated in one direction and the slide is accelerated in the other direction.

And this backward and forward acceleration is brought about by force.

Regardless of what else the pistol does once it's moving...it all starts with force. Force forward and force backward.

Yes? No?

If it's YES, we have a consensus. If it's NO, then you're gonna need to explain what...besides force...will move the slide.

 

[Jlr2267]

{The question is whether gas pressure is directly harnessed to make them work. In the case of gas pistons and blowback, gas is used directly. In the case or recoil, the gas pressure has created acceleration of both barrel/slide and bullet. That recoiling movement is what unlocks and extracts the casing. Gas is no longer a factor at that point.}

That is what both sides have been saying all along, and it is correct. The expanding gas provides the energy for operation in both systems, and I think that is what 1911_Tuner was saying (at least, that's how I read it).


{That's what 45auto and I have illustrated with examples of the forces involved, how recoil operation can be created without gas pressure and how recoil forces are unnecessary to make blowback go.}

This is where the confusion is coming in (and it is mostly semantics, I think). There is no recoil force without expanding gas *in the designs being discussed*. Yes, you can design a magnetic gun that recoils without gas pressure, and you can also design a magnetic case that would operate a blowback gun, but those are not the designs being discussed.

{You can say they are all the same, but they are only the same in ways that have nothing to do with their individual definitions. Blowback and recoil are separate terms because they do, in fact, describe different uses of energy in a mechanical system. If they were the same, they'd have names that reflected that and would behave the same under our examples.}

I completely agree that definitions are being abused. That stated, there are though, very fundamental similarities in the actions, the primary one being that both actions are initiated via gas pressure alone, and nothing else. Gas pressure provides the force to accelerate the slide rearward in both actions being discussed.

 

[tark]

Tuner, this is the second time you have posted your Fluroscope picture...why don't you post the rest of the pictures in the series? Yes, there are more. Post the one where the bullet has left the muzzle, and penetrated five or six thin sheets of tin that were placed about a foot from the muzzle. You will see in that picture that the slide is just barely starting to move. I am STILL waiting for someone to show me 10,000 frames per second photography showing ANY movement of the slide on ANY automatic until AFTER the bullet has left the muzzle. I have found a few close ones where the bullet was only about a foot away from the muzzle. These were invariably the short barreled compacts, but I have yet to see a slide move before the bullet exits.
I guess my point is; if nothing is moving before the bullet has left town, why do you need a locked breech at all? I have seen pictured of crude copies of 1911s , made in third worlds countries that have no locking lugs at all on the barrel, They look terrible, but they function, quite well. And yes, they were .45s.
Actually, I believe someone is making a .45ACP pistol that is a Blowback.. Working in a 1911 shop, I don't have much exposure to anything else. (or much interest, for that matter)
I have one other bone to pick. Surely I misread you, or did you actually say that someone completely obstructed the bore on a 45 with a threaded plug, which rested against the bullet, matching its contours perfectly, chambered a hardball and fired the pistol and nothing happened?????
I find that very hard to believe.

 

[45_auto]

I think that is what 1911_Tuner was saying (at least, that's how I read it).

You're just not familiar with how confused 1911tuner is. You can't explain it to him with words, he doesn't understand the terminology.

You need to go back to all his previous incorrect posts on barrel friction, how a 1911 is really delayed-blowback operated, etc. He doesn't understand recoil and how a 1911 operates.

For example, the "short recoil" thread (which inspired this thread), post #9:

http://www.thehighroad.org/showthread.php?t=735059&highlight=recoil+operated

Even a straight blowback is recoil operated.

And the locked breech, recoil operated pistol is technically a delayed blowback.

 

[1911Tuner]

This is where the confusion is coming in (and it is mostly semantics, I think). There is no recoil force without expanding gas *in the designs being discussed*.

YES! YES!

Recoil is acceleration in the other direction and acceleration is only brought about by force.

Lemme do this in layman's terms.

Newton 1:

If ya want it to move, ya gotta push it. When ya push it, ya get pushed in the other direction...by force in the other direction.

It don't make no never mind what kinda gun it is. It ain't gonna operate 'til the slide moves, and force backward is the only thing that'll make the slide move backward.

Recoil forces if that makes ya'll feel any better.

That's all I've been tryin' to say.

Now, if there's somethin' else that'll get the slide movin' I wanna know about it.

 

[1911Tuner]

And the locked breech, recoil operated pistol is technically a delayed blowback.

And it is. The slide is "blown back" by expanding gas and force, no?

And it's delayed...no?

They're ALL delayed by some means. They have to be.

The only real difference is the method or the device used to effect that delay.

 

[Hurryin' Hoosier]

All I know is that my pistols go "bang" every time I pull the trigger and keep feeding them cartridges, and I damn sure don't plan to weld a plug into any of my barrels.

[This thread is] but a walking shadow, a poor player, that struts and frets his hour upon the stage, and then is heard no more; it is a tale told by an idiot, full of sound and fury, signifying nothing.

 

[45_auto]

And now we've come full circle and back to the original points that got all this mishmash started.

Does this mean that you are willing to name your bet and give your odds now?

 

[tark]

Tuner, I see you have made a post after I have, so I assume you have read it. I await answers.
Are you saying that the plugged bore pistol, DIDN'T blow out the bottom of the case where the feed ramp is ????

 

[45_auto]

All I know is that my pistols go "bang" every time I pull the trigger and keep feeding them cartridges

Yeah, but not all of us are like you and are satisfied depending on "magic" to make stuff work. Some of us have to actually design guns, rockets, and other systems to defend our country based on Newton's laws. If you're not interested in how they work, feel free to put me on "IGNORE"!

Next we'll move up to a blowback pistol. Notice how the barrel is pinned to the frame, while the breech block (slide) is free to move:





Does anyone have any doubts as to what is moving the slide rearwards on this gun? If the breech of the barrel was welded shut (hint, it would work very similarly to the gun in Figure 2), would the slide move?

 

[1911Tuner]

Are you saying that the plugged bore pistol, DIDN'T blow out the bottom of the case where the feed ramp is ????

Nope. It didn't. Contact Jim K for verification.

And I duplicated it a few years back. Nothing happened. Nothing moved. All the gun did was sit there and hiss as the gas vented around the breech.

45 Auto...

Go weld up the back of the chamber and make sure the plug is against the breechface when you light the charge. Since you're so
invested in this, I want a video...from assembly to bang.

Now, think about it. Is your welded plug hypothesis any different than a muzzle loader? By your theory, the musket shouldn't recoil.
But as anyone who's ever fired one can attest...they recoil just fine.

 

[tark]

One more thought on that fluroscope picture, That gap you see between the top of the lugs and the slide would seem to indicate the slide has moved slightly and the barrel is beginning to drop.... Sorry guys. Most 1911s (like, almost all of em) have that gap with nothing going on at all. The top of the lugs must NOT touch the slide. If they do, and the pistol gets too hot, it can freeze up the gun, or at least make it cycle sluggishly. Also, I have a GI 1911 where the back of the slide hangs off the frame by about .80 thousands. Take a picture of it from the side and it would look like the slide has started backwards. I see no movement by the slide in the Fluroscope .

 

[tark]

All right , Tuner, if the primer ignited the powder, what happened to the pressure generated. Who is this guy and how do I get a hold of him?

 

[Jlr2267]

I think the people who wrote that engineering book believe it, too.

Recoil occurs when a force is expended between two (or more) objects that then become projectiles moving away from each at the same momentum. The source of that force doesn't matter as long as it acts on both halves. Crossbows recoil, open bore rail guns recoil, low pressure long barrel guns recoil.

Bazookas and other rocket launchers don't recoil because the force expended is not in opposition to the launcher that fires the rocket. But guns, regardless of the amount of residual bore pressure when the bullet exits, all recoil away from the projectile. That recoil is harnessed in recoil actions to drive an unlocking and extraction mechanism.

In gas piston actions the bore gas pressure is harnessed to drive an unlocking and extraction mechanism.

In blowback there is nothing to unlock and the casing is extracting itself under its own pressure.

I think you are misreading the book. Gas pressure forcing a bullet down a barrel does not cause recoil *of the barrel*, unless whatever is at the breech, absorbing the force of gas pressure, is mechanically locked to the barrel.

Gas pressure acts on the barrel only in the *radial* direction, causing expansion of the barrel...it imparts zero force (on the barrel) in the direction of the bore axis (although there is the bullet/bore friction, but it's somewhat irrelevant)

 

[45_auto]

Of course your welded plug straight blowback won't cycle. You're using the plug for a breechblock instead of the slide, and the barrel is attached to the frame. The slide would feel no force.

You do understand that the slide is a breechbolt.

And I'll bet money and quote odds that if you do the same with the barrel in a recoil operated pistol...you'll get pretty much the same results, though the slide will move a little because the barrel will move and push the slide. It won't make full cycle, though. Bet on it.

45 Auto...

Go weld up the back of the chamber and make sure the plug is against the breechface when you light the charge. Since you're so
invested in this, I want a video...from assembly to bang.

No problem with the video. What's the bet and what are the odds you're offering?

Now, think about it. Is your welded plug hypothesis any different than a muzzle loader? By your theory, the musket shouldn't recoil.

You really should read more slowly. I'm the one that told you that the welded-breech barrel would recoil and take the slide with it to function the weapon.

Short Recoil thread, post #20 is what started the whole bet scenario you welched on:

You could weld a plug into the back end of the chamber of your 1911, load it from the front with blackpowder, and it would cycle perfectly normally. Slide will cycle, hammer will cock, etc. That's because it's RECOIL operated.

 

[1911Tuner]

One more thought on that fluroscope picture, That gap you see between the top of the lugs and the slide would seem to indicate the slide has moved slightly and the barrel is beginning to drop.... [quote/]

Nope. The link doesn't start to tug on the barrel until it's moved backward about .100 inch.

Gas pressure acts on the barrel only in the *radial* direction, causing expansion of the barrel...it imparts zero force in the direction of the bore axis

Uh...

If the pressure doesn't exert any force in the direction of the bor axis...

...what pushes the bullet through the bore?

Pressure imposes force in all directions at once. Up, down, sideways...forward and backward. Because it's exerting those forces in a barrel, it becomes a vectored force..."vectored" describing magnitude and direction. Unless the barrel splits, the directional force is forward and backward.

 

[1911Tuner]

No problem with the video. What's the bet and what are the odds you're offering?

Oh, why muddy it up with money/incentive. Do it for the sake of science. Do it for the fun. Do it because you're so hungry to prove me wrong. Make sure the plug is touching the breechface.

But think about that musket before you warm up the welder.

 

[RX-79G]

JR,

The point is and has always been whether "blowback" and "recoil" are the same or different in their effect.

They are the same in that all guns have all or some parts that are pushed opposite the bullet when gas expands between them. No one is arguing this point at all.

The central argument is whether a recoil pistol "blows back". And here's where the disagreement and confusion lies:

The definition of "blowback" or "blowforward" is that gas pressure acts directly between the bore and casing, forcing the casing out of the chamber. That can only happen if the breech is an unlocked type.

So when someone (1911tuner) calls a recoil operated pistol "blowback", he is observing that gas powers the action, but ignoring the fact that the term is used to describe the forces that cause extraction, not overall operation.

The term "recoil operated", in contrast, describe how firing energy is transformed from pneumatic to mechanical in a way to unlock the action and extract the case by secondary means. It is not able to "blowback" the casing by virtue of being locked at time of firing, so we do not call it blowback. That mechanical energy is from a recoiling mass, hence the term "recoil". That mass can be made to recoil from a variety of propellant means that don't have to be gas pressure, which illustrates the point further that the blowback derived energy part is unnecessary in the definition.

When a Luger unlocks, the chamber pressure in the casing is at sea level. It is difficult to argue that the extraction at that point is "blowback". The blowing has run it's course, and energy has been stored and released on the case by different means.


Further confusing things is 1911tuner's insistence on re-purposing the term "delay" from "delayed blowback" to mean "the time an action remains locked". The word delay is being used in entirely different ways - one describes a relative cessation of motion, the other a change in rate during constant motion. The second definition is the one we, gun people, use. Misusing it creates confusion.


Why does this stuff matter? Because if you think a 1911 can only work correctly with barrel friction, you will never understand how a FN FiveSeven works. And if you believe that a blowback gun can't be locked without being called recoil operated, you'll never understand how a Benelli inertial shotgun works. Both of these guns have locked breeches but blowback for extraction. Neither require slide mass in direct proportion to the momentum of the round fired.

 

[45_auto]

But think about that musket before you warm up the welder.

Why do you believe that a musket barrel recoils but a 1911 barrel with a welded breech (a muzzleloader by any other name) won't?

 

[Hurryin' Hoosier]

Some of us have to actually design guns, rockets, and other systems to defend our country based on Newton's laws.

Oh, damn. Sorry. I didn't realize whom I was dealing with. I trust that my post wasn't intercepted by the NSA.

 

[Jlr2267]

Uh...

If the pressure doesn't exert any force in the direction of the bor axis...

...what pushes the bullet through the bore?

Pressure imposes force in all directions at once. Up, down, sideways...forward and backward. Because it's exerting those forces in a barrel, it becomes a vectored force..."vectored" describing magnitude and direction. Unless the barrel splits, the directional force is forward and backward.

It does not impart a force *on the barrel* in the axial direction