Dummy that will cycle the slide

[wagoneer1019]

I have heard from some former LEO's in the pre-taser days of the 1970 and 1980's they yould have snake shot the first round up in there revolvers as a less leathel option and the shot-gun affect of not missing. what do you think? out in the desert I will have snake shot for rattle snakes, and took a rabbit with it once but it took 2 rounds to do the job, so it will draw blood but its kinda weak

 

[kingpin008]

I dunno about you, but if I have to shoot someone to stop them from being a threat to my or my family's life, I don't care about wounding them. I care about incapactitating them. That means making it physically impossible for them to keep moving - snake shot will not do that.

Look - if you shoot at a badguy with some sort of less-than-lethal round (rubber bullets, snakeshot, rock salt, whatever) and you wound the hell out of him and he stops, fine. Awesome. But be prepared to sit in court and justify to his lawyer and a jury how you felt the need to pull a gun on this poor, disadvantaged, misguided inner-city youth yet you weren't in sufficient fear of your life so you used non-lethal ammo.

I can almost guarantee you they'll tear you apart.

 

[akodo]

If you aren't in such immediate danger that you need a REAL gun with REAL ammunition, then aren't in enough danger to use a bluff gun and fake bullets

 

[KelVarnson]

I think this should be theoretically possible with blowback style actions (it might not have even been done successfully).
If the cartridge has a properly designed nozzle to achieve correct chamber pressure, you should be able to simulate the pressure response to a normally fired round. This is clearly going to be more complicated than a simple crimped case or wax plug - and probably far from cost effective (see Gyroget)

As for gas operated designs like an AR, AK, SKS, or FAL, the only way to cycle a blank will be with a blank adapter as the action cycles on pressure in the barrel and not at the chamber (the blank adapter will have to be removed prior to firing any real bullets, or else you will have kaboom in your face).

Very interesting comments! I was thinking in terms of recoil-operation, not blowback or gas. You may have surmised that. Thanks for making me think about it some more.

 

[baryon]

http://video.google.com/videoplay?docid=6153240995617731728&vt=lf&hl=en

If coke+mentos can propel a bottle, I think a 9mm or .40S&W cartridge should have enough power. don't you think? Now, who is going to try it at a gun range?

 

[NeoSpud]

Baryon, you're missing the point. Let me put it this way: if you dropped a mentos into a glass of diet coke, what'll happen? It'll fizz over, not moving the glass one bit. The bottle in your video moves because of the gas trying to escape the constricted "nozzle" where the cap screws on. That's how blank firing adapters work, generally speaking. Without the BFA, which would make shooting conventional ammo immediately afterwards impossible, it just won't work with 9mm and .40S&W.

AFAIK, the gas will simply follow the path of least resistance, right out the barrel, without imparting significant rearward force to move the slide and chamber a new round.

I could be way off here, of course, but it just doesn't seem feasible (or smart, tactically).

 

[kcshooter]

If coke+mentos can propel a bottle, I think a 9mm or .40S&W cartridge should have enough power. don't you think? Now, who is going to try it at a gun range?

Not a physics major, eh? Every action has an equal and opposite reaction. The action created by the blank doesn't create a reaction strong enough to overpower a recoil spring. It just won't work, period, no need to try this one at the range.

If the cartridge has a properly designed nozzle to achieve correct chamber pressure, you should be able to simulate the pressure response to a normally fired round.

What chamber pressure? You can't pressurize an open tube.



Also, what the hell is a "warning shot"??

 

[Frank Ettin]

[1] Fpr every action there is an equal and opposite reaction. The energy of the "action" is a function of the mass shot down range. The reaction is equal to it and is necessary to make the gun cycle. The mass sent down range when firing a normal cartridge is the bullet plus the mass of he gas created by the burning of the propellant. The mass going down range when firing a blank is merely the mass of the gas. This is a substantial difference and makes a substantial difference in the energy of the "reaction." The former can cycle the gun. The latter can not.

[2] In order to make guns cycle with blanks for the movies, the special effects wizards modify the gun by constricting the bore and using a light recoil spring. These modifications are incompatible with firing live ammunition.

 

[protolith]

If the cartridge has a properly designed nozzle to achieve correct chamber pressure, you should be able to simulate the pressure response to a normally fired round.

What chamber pressure? You can't pressurize an open tube.

Think of how a blowback action works. As the powder is burning the expanding gas forces the bullet down the barrel and the chamber pressure initiates the cartridge pushing on the slide, the bullet exits the barrel and the combustion ends, the inertia initiated during combustion continues and carries slide back to the stop, the casing is ejected and the recoil spring returns the slide.

This all requires proper timing and a proper balance between chamber pressure, recoil spring tension, and balance with the slide, powder load, bullet weight, etc.

The reason simple blanks don't work is without a slug forming a partial seal in the barrel while being propelled down the barrel the normal chamber pressure is not achieved. A blowback design firing blanks only works with a much softer recoil spring.

From your statement, I assume you already know this part.

Now to make a blank that will cycle a regularly set up blowback action (standard recoil spring), we will need a specially designed casing with a much thicker casing wall and a nozzle in the end so the correct chamber pressure occurs within the casing. The thicker casing wall will attempt to contain the pressure long enough to at least initiate the action and the gun will cycle as designed.

I am not trying to suggest this would be trivial to develop. In fact I think it would be quite difficult to get the balance with the thickened casing wall, nozzle opening, temporary sealing technique (small wax plug, or some sort of crimp past the nozzle) and finding the right rate of powder burn to generate a proper recoil impulse. All without blowing itself up or shooting the primer out of the pocket.

The main reason this has never been properly developed (as far as I know) is likely due to the fact that there is really no good reason to mix banks and real rounds in the same gun, In fact I agree this is a tactically dangerous proposition. It makes better sense to require either modification of the gun (weaker recoil spring) or installation of a blank firing device to ensure that there is no confusion as to the state of the firearm, blanks for training, or real ammo for intended purpose - and never the two mixed. Thus its not worth the effort to engineer when a simpler method of firing blanks already exists.

So I again submit that it should be theoretically possible (in blowback designs) to engineer a blank round that will properly cycle.

If your statement:

What chamber pressure? You can't pressurize an open tube.

was regarding gas operated designs that bleed pressure from ports in the barrel like the M1Garand/M1carbine/M14/M1a/mini14 design or the AR (stoner) design or the AK/AKM (Kalashnikov) design or the FAL/G1/G3 design or any other gas operated design. I agree that no amount of special blank design will work without chamber restriction in the barrel somewhere past the gas port. Reread my post and you will see I stated this.

 

[FSCJedi]

Not trying to sound like a smart a$$ here, but you guys who are trying to figure out the mechanics of this blank cartridge that cycles the slide are just enabling the OP...

*shrug* Just my $0.02.

 

[.cheese.]

protolith - I'm not following you.

It sounds like what you're thinking of is making a cartridge that works like a little rocket pushing backwards on the slide. I'm not fully grasping what the thicker casing has to do with it though?

Also, somehow I just don't think you could do that in a safe way.

1) You'd need a lot of energy/powder

2) What happens during ejection? The cartridge would basically be a gyrojet projectile flying backwards at the shooter. So you'd shoot yourself or some guy to your side.

Might as well just go all the way with that concept:

 

[baryon]

Not a physics major, eh? Every action has an equal and opposite reaction. The action created by the blank doesn't create a reaction strong enough to overpower a recoil spring. It just won't work, period, no need to try this one at the range.

Studied Engineering. May be I slept in Physics class My Coke bottle analogy is not bad. If the liquid propellant coming out at low velocity can propel a heavy bottle(heavier than a slide) up in the air, is it not feasible that the gun powder in a cartridge that is fully burnt in about 15ms generates enough pressure to move the slide by 3 inches? The slide hasn't got to slam back. Just enough velocity to eject the empty cartridge and clear the top of the magazine.

A quick search shows that thrust is dm/dt*v where dm/dt is the rate of change of the mass of the propellant coming out and v its velocity. The key is to find these values so that it can overcome the recoil spring + slide.

I think the front portion of the cartridge may have to be shaped so that it behaves like the nozzle of a rocket and acts like a micro rocket pushing the slide back.

 

[baryon]

and finding the right rate of powder burn to generate a proper recoil impulse.

You might have a point there.

 

[kcshooter]

You aren't getting it. You can't simulate chamber pressure within the cartridge. The pressure needs something to push against, an obstruction within the barrel. Be that obstruction a bullet or blank adaptor or some other type of plug, you need something for the force to push against to move the slide. It just simply won't work. It would require a dangerous amount of explosive force to get it to move even a slight amount. To equate it to a bottle analagy requires a much longer buring period and no force acting upon the slide to keep it in place, so while this may work to open the slide slightly with no recoil spring in place, it wouldn't close itself again, and would not have the force required to eject the casing. Once it moved back slightly, with no recoil spring mind you, enough to free the cartridge, you are again dealing with a completely open tube. Therefore, no pressure.

 

[KelVarnson]

Even open tubes have resistance to flow, if the pressure is high enough.

 

[kcshooter]

Even open tubes have resistance to flow, if the pressure is high enough.

Yeah, now how much explosion would you have to have in your hand to get enough resistance to overpower the slide and recoil spring by creating enough pressure within an open tube.

Wow.
OK, if you think I don't know what I'm talking about, try it. Give it a shot. See what happens.

 

[Joey_the_Wolf]

Two hollowpoints to center mass should serve as a warning. If the perp still doesn't get the point, a well placed shot to the head, preferably severing the Medulla Oblongata, should resolve the situation. As many have stated here, warning shots will do you more harm than good in a self defense situation.

 

[Frank Ettin]

I'm backing kcshooter.

There are two ways to make a semi-auto work: gas pressure, like the piston in a car engine; and Newton's third law, "for every action there is an equal and opposite reaction."

Some guns do indeed work by gas pressure, the AR-15 for example. In those guns some of the propellant gas is bled off into a cylinder closed at one end by a piston that can move. As the pressure in the cylinder increases, it moves the piston, which moves an actuating rod to operate the action of the gun. Moving the piston requires forcing a large enough volume of gas into a small enough space. Pressure is a function of the volume of gas and the space confining it. A given volume of gas in a large, or rapidly expanding space, produces less pressure than the same volume of gas in a smaller, or slowly expanding space.

The other way is the opposite force created by firing the gun and shooting something forward. The opposite force is a function of the amount of mass going forward and the velocity of the mass going forward. Shooting a greater mass at a given velocity produces more rearward "recoil pulse" than a lesser mass at the same velocity. This is how a jet engine works. The engine expels to the rear a large mass of gas at very high velocity, and that produces a large enough opposite (forward) force to overcome the vehicle's inertia and move it forward. The exhaust doesn't push against anything.

But to make a recoil operated gun work, the amount of mass sent forward and its velocity must be sufficient to generate a large enough opposite force to overcome the forces holding the gun closed. In an auto-loading pistol, those forces to be overcome include the inertial mass of the slide, the recoil spring and, in a locked breach pistol like a 1911, the force exerted by the locking lugs.

Firing a regular cartridge, by far the largest component of the total mass going forward is the bullet. If the bullet were absent, such as in a blank cartridge, the mass of the gas going forward would have to make up for all, or most of the mass that would otherwise be provided by the bullet. That would be a huge volume of gas because the gas is far, far less dense than the material of which the bullet is made.

(BTW, a blow back pistol also operates from recoil pulse, not pressure. The defining characteristic of a blow back design is that the breach is not locked mechanically, and the action is held closed solely by the recoil spring. The pressure of the expanding propellant gas is not a factor. While the expanding gas does no doubt exert some pressure on the breach face, the size of the area into which the gas is expanding is rapidly increasing, effectively to infinite, as the bullet moves down and exits the bore. Therefore, the pressure falls off very quickly.)

Hollywood special effects wizards modify a pistol to cycle with blanks by constricting the bore to slow the drop off of pressure. They may also use very light recoil springs. A blank actuated gun thus works from pressure, but the modifications are certainly incompatible with live ammunition.

Of course, if someone thinks he can produce a blank cartridge that will create a large enough mass of gas moving forward at a high enough velocity to generate a sufficient recoil pulse to cycle a semi-automatic pistol, he's welcome to try. I'd be very curious to hear how it works out.

Even open tubes have resistance to flow, if the pressure is high enough.

Of course there are substances which, when ignited, will produce a large enough volume of gas quickly enough to produce appreciable pressure even when not confined. I think, however, that C-4 would be a poor choice for a propellant for a blank cartridge.

 

[ny32182]

Baryon, the only way the powder burns in milliseconds is if there is an obstruction in the bore (either a bullet or blank firing adapter) that will raise the pressure exponentially as the reaction begins. I guess a chemistry lesson you missed is that stuff burns much faster under high pressure. If you burn a pile of powder in the open air (essentially the same thing you are doing if burning it in a chamber with no bullet present), it will not burn quickly at all relative to the way it burns in a live round. It may take 1-3 seconds or more to burn depending on the powder. I know, because I've lit many small piles of powder in the open air.

Your coke bottle analogy is more akin to having a blank firing adapter installed: The space for gas to escape is much smaller than the diameter of the bore/chamber; therefore a little pressure builds as the gas escapes. Enough to move the bottle. Enough to move the barrel, and thus the slide with a super-light recoil spring installed, in a blank firing gun.

If you are firing a blank with an open bore (no adapter installed), the analogy is what someone mentioned earlier: You are dropping a mentos into a rock glass with coke in the bottom: The opening for the gas to escape is the same diameter as the bore/chamber. No significant pressure builds. No kinetic energy is imparted to the barrel. None. And the recoil spring/lockup of a real pistol is a whole lot stronger than it is in a blank firing pistol.

 

[KelVarnson]

(BTW, a blow back pistol also operates from recoil pulse, not pressure.

Where do you think the "recoil pulse" comes from? It's from the expanding gas pushing between the bullet and the case. ALL of the energy that goes into moving the slide back comes from the expanding gas.

The pressure of the expanding propellant gas is not a factor. While the expanding gas does no doubt exert some pressure on the breach face, the size of the area into which the gas is expanding is rapidly increasing, effectively to infinite, as the bullet moves down and exits the bore. Therefore, the pressure falls off very quickly.)

I think you meant to say the "volume" into which the gas is expanding. Nonetheless, ALL of the energy imparted into the slide moving back and the bullet moving forward comes from expanding gas. True, as soon as the bullet leaves the barrel, the pressure drops drastically, but at that point the vast majority of the energy from the expanding gas has already beeen imparted into the slide and the bullet, and they keep moving in opposite directions.

In the OP's example, if there is no bullet mass/inertia to push against, the gas pressure will not get high enough to impart sufficient energy into the slide to cycle the action. I get that. In my previous statement, I was only saying, that pressure will not be zero just because the tube is not restricted. There will still be a pressure pulse, due to the inertia of the air/gas itself and the resistance to flow due to friction in the open tube.

 

[Frank Ettin]

Where do you think the "recoil pulse" comes from? It's from the expanding gas pushing between the bullet and the case....

It absolutely does NOT, at least if you're trying to say that the pressure of the expanding gas is what actuates the action of the pistol. A rocket engine with work in the vacuum of space where there is nothing for the exhaust gases to push against. It is simply that the force accelerating the gases to the rear also produces an equivalent forward acceleration.

The bullet is propelled forward by the expanding gases. But the recoil pulse is not produced by the pressure of the gas. As set out in Newton's Third Law, the force that accelerates the bullet forward produces an equal and opposite acceleration which is the rearward recoil pulse.

A relatively larger force is necessary to accelerate a relatively massive bullet, and a significantly less massive volume of gas, forward; and the force will be the same to the rear and accelerate the mechanism of the pistol to the rear. The force accelerating something far less massive, like simply a quantity of gas. will be considerably less.

While the pressure of the expanding gas is the motive power for the bullet, the recoil pulse is not produced by the pressure directly. It is an artifact of the forward acceleration of the bullet.

 

[KelVarnson]

The bullet is propelled forward by the expanding gases.

Agreed.

As set out in Newton's Third Law, the force that accelerates the bullet forward produces an equal and opposite acceleration which is the rearward recoil pulse.

Agreed. And with the combination of these two statements, you have just said that it is the expanding gas that propels the slide back. And you are correct.

The expanding gas from the burning gunpowder is the ONLY source of energy in the gun. All of the energy that it takes to move the slide back comes from this expanding gas.

But it is an equal and opposite reaction. The amount of energy imparted into the bullet (during the time its in the barrel) by the expanding gas should be equal to the amount of energy imparted into the slide. Of course, some of the energy put into the slide moves the rest of the gun, too, since the slide and the gun are connected. But, all of the energy moving the bullet forward and the slide backwards comes from expanding gas.

 

[NG VI]

In a SD situation may be it can be used to fire a warning shot

Terrible idea. If you need to warn someone off, do it by directing their eyes straight down the bore and instruct them that the flightplan of the next few moments depends entirely on their actions.

 

[Sean Dempsey]

Every single instructor for CCW has advised against warning shots.

It's a decent theory, but a horrible practice.

You fire a shot - everyone thinks its real. Now, instead of surrendering, the badguy feels he's being shot at and is going to die! So now he fights back with his own weapon and gun, assuming you meant to kill him.

It's like pretending you know karate to stop a fist fight.

 

[jordan1948]

My suggestion, if you don't want to use lethal force get a shotgun and some rubber buckshot or slugs.