Suppressor that closes after bullet leaves?

[RTR_RTR]

http://www.youtube.com/watch?v=otpFNL3yem4

I think it would be particularly tricky given that gas (albeit lower pressure) escapes ahead of the bullet as well

 

[JustinJ]

I think it would be particularly tricky given that gas (albeit lower pressure) escapes ahead of the bullet as well

Certainly all gas could not be captured. Existing air in the barrel will of course get compressed by the bullet and some gas may leak past due to grooves from rifling however i think this is extremely minimal. The question is could the trap close fast enough to capture enough of the gas to suppress better than a conventional baffle method.

 

[SharpsDressedMan]

I actually saw the drawing of it, and it was like a piston chamber inside the suppressor that opened the holes to the chamber when the blast hit it, and then the spring rebounded, and the chamber moved to seal the expanded gases in. Bear in mind, it didn't trap ALL the gases; there were baffles forward of the piston/chamber.

 

[jmorris]

The question is could the trap close fast enough

Check valves commonly used for compressed gases work at the rate of opposing flow. I think "the question" is back on post #15, can you design a valve that would not close before the bullet passes but close before all the gas excapes. If the valve closes from the air moving infront of the bullet your out of luck.

 

[SDC]

Humbert, a Frenchman, came up with this basic idea in 1898; he proposed designs for both artillery and small arms, but I don't know if any were actually built. He suggested using either a "clapper" that would be sucked closed by the passing bullet/shell, or a lightweight ball that would do the same (but I don't know what he would have suggested if you had to fire downhill). This photo is from Semyon Fedoseyev's "Spetsnaz Oruzhie"/"Special-purpose Weapons".

 

[JustinJ]

Good find, SDC. Thanks for the pic. The ball idea is very interesting and not something i ever considered.

 

[jmorris]

Thats how many check valves work but me either...

 

[JustinJ]

Thats how many check valves work but me either...

True but the method above essentially turns the entire can into a check valve.

 

[flatlander937]

Not sure what kind of firearm you're looking to put it on but thinking off the top of my head...

but If there were a large "flap" on the end that is under spring pressure(it swings OUTWARDS away from the muzzle), what if a small gas chamber were routed from the barrel(roughly mid-way... bullet needs to get moving first) outwards to the flap so that the pressure forces it outwards... as long as the gas tube is sized right, and the actuating portion is sealed well enough, then pressure should still remain in the barrel overall until the bullet leaves the muzzle, at which point pressure will equalize and it will close again.


You could also substitute the "flap" idea with a "sliding" blocking plate actuated by piston(s) and it would function the same.


That said, I don't think ANY idea will FULLY close the suppressor in question and gas will need to be allowed to leak out due to pressures inside the barrel.


Something a bit more doable(albeit not fully mechanical if that's something you're after) might be to drill a gas tube to host a piston, and use that piston to actuate an electronic microswitch that will control a solenoid valve that will actuate the blocking mechanism(whether plate or tilting whatever you decide on).


Just throwing some ideas out there

 

[JohnKSa]

If this thing can actually be made to work, it's going to be problematic with semi-auto rifles. You won't want to eject the cartridge while there's pressure still being held in the chamber/bore.

 

[RTR_RTR]

Check valves commonly used for compressed gases work at the rate of opposing flow. I think "the question" is back on post #15, can you design a valve that would not close before the bullet passes but close before all the gas excapes. If the valve closes from the air moving infront of the bullet your out of luck.

Yes, that was my concern - it ups the trickiness factor of an already very finicky set up - would have to cut a very narrow window of pressure

 

[JustinJ]

but If there were a large "flap" on the end that is under spring pressure(it swings OUTWARDS away from the muzzle), what if a small gas chamber were routed from the barrel(roughly mid-way... bullet needs to get moving first) outwards to the flap so that the pressure forces it outwards... as long as the gas tube is sized right, and the actuating portion is sealed well enough, then pressure should still remain in the barrel overall until the bullet leaves the muzzle, at which point pressure will equalize and it will close again.

Do mean an external flap? Interesting idea. Also if the system malfunctioned the bullet would likely be able to force its way through if designed accordingly. If attached externally it may also allow for a retrofit to existing cans although a gas tube running outside may not be ideal. It would certainly make it easier to test the concept.

A good question is would installing a flap to the exterior of an existing can require any sort of registration with the ATF.

If this thing can actually be made to work, it's going to be problematic with semi-auto rifles. You won't want to eject the cartridge while there's pressure still being held in the chamber/bore.

I think the question will be how much pressure would remain during ejection as opposed to if all is gone.

 

[JohnKSa]

There's enough pressure remaining in the bore to make a sound like a small explosion or this entire discussion would be moot, right?

I wouldn't want that much pressure propelling an empty case out of an open action nor acting on a bolt that has unlocked in preparation to eject the fired cartridge.

 

[JustinJ]

There's enough pressure remaining in the bore to make a sound like a small explosion or this entire discussion would be moot, right?

Use of a convential suppressor can increase ejection force due to back pressure. The question is whether or not the pressure falls to within acceptable levels in time. Trapped expanding gas from combustion does not remain at high pressure indefinitely.

 

[JohnKSa]

Trapped expanding gas from combustion does not remain at high pressure indefinitely.

An action typically unlocks and ejects within just a few milliseconds--not exactly "indefinitely".

Use of a convential suppressor can increase ejection force due to back pressure.

Sure, but a conventional suppressor is trying to give the gases a place to go so other than out the muzzle and to slow the escape of the gases. It's not trying to trap them outright. There's a huge difference in the two functions.

But yes, even the relatively small increase in back pressure due to a suppressor can have an adverse effect on function. If one could actually manage to trap the gases with a valve, that would cause much higher pressures.

 

[Brockak47]

Even if it were possible sounds like it would be prone to breakage.

The gas trap rounds sound neat, going to have google up on those

 

[JustinJ]

An action typically unlocks and ejects within just a few milliseconds--not exactly "indefinitely".

And gas pressures from combustion, even if trapped, rapidly decay. I do not know if they do so fast enough or not and it is a valid concern. Obviously the can would not be able to trap all gases. It may be an issue in some guns and not others or may require an adjustable gas system. For example, a 20" ar may work but not a 14.5".

Even if it were possible sounds like it would be prone to breakage.

I think that depends completely on how the thing works. Modern materials certainly make it more feasible today than in the past.

 

[dprice3844444]

best thing is the kiss principal on suppressors.if there is moving parts,they will break at the most inopportune time.they have to be made indestructible and as sturdy as possible as field oporatives who would be using them in most cases would not be mechanically inclined and unable to do field repair.

 

[flatlander937]

I was referring to an external flap as you thought...

My thinking isn't so much to stop all gasses(not going to happen), but the flap may assist in directing the gasses(and sound) downwards... similar to cupping your hands to throw your voice in a similar direction(and consequently lowering the volume in other directions).

It could also go upwards if you wanted... depending on if you're shooting indoors or out would probably make you choose to do one or the other.

Worst case scenario, maybe the bullet hits the flap and it breaks(I'd recommend something LIGHTWEIGHT so it is more likely to be moved by the bullet IF this were to happen than if it were heavier).


On a related note... ASSuming you're trying to make it quieter so it's less detectable for whatever it is you're shooting AT... why not build a suppressor like normal, with a muzzle-brake on the end to redirect the remaining gases?

Depending on how it is dispersed, I imagine with a large enough brake, with pressure relief holes/slots/whatever all the way around the circumference of the barrel, in my head it seems it would make sense that by redistributing the sound of the propellant gases to go in all directions(instead of just forward from the muzzle) it may be quieter for anyone in front of the muzzle... maybe with a slight increase in noise from behind/to the side of it though.

Again, just thinking out loud.

 

[JohnKSa]

And gas pressures from combustion, even if trapped, rapidly decay. I do not know if they do so fast enough or not and it is a valid concern.

For safety, the chamber is not supposed to open/the action is not to unlock until the bullet has left the bore.

If this device is fast enough to trap enough pressure to significantly reduce the report, it will also cause the barrel pressure to stay at levels high enough that it would be unwise to unlock the action/open the chamber until that pressure is reduced. If this device is to be useful for its intended purpose, it will not be applicable to semi-auto actions because they open the action very rapidly. That's without getting into the issues involving what retaining pressure in the barrel would do to a gas system.

By the way, I'm still predicating all my responses with "If" because I still don't think it's feasible in the first place. I'm just pointing out that even if it were somehow manageable, it would cause other problems in certain types of actions.

 

[JustinJ]

My thinking isn't so much to stop all gasses(not going to happen), but the flap may assist in directing the gasses(and sound) downwards... similar to cupping your hands to throw your voice in a similar direction(and consequently lowering the volume in other directions).

Couldn't you get the same effect with just a hood protruding out over from the top of the can?