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Old April 24, 2021, 02:54 PM   #1
simonrichter
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Captive piston silent ammunition

the Russians use this captive piston "silent" cartridges for their special ops, and something like a silent shot revolver basrd on the same tech has been conceived but never mass produced for Vietnam tunnel rats. I still can't wrap my mind around how this principle can produce more that air gun pellet muzzle engergy: In a normal gun, the powder does not just "explode" like firearm newbies may think, but the powder still burns while the bullet is already driven through the barrel, - thus the whole issue of barrel length, fast / slow burning powder etc.

All this considered, how can a device where the bullet only ever gets an impulse, without any pressure building up in the barrel, drive a bullet through the rifling, overcoming the friction (the "tunnel rat" revolver was smooth bore, but the Russian pistols do have rifling) and still produce muzzle energy to speak of?

very special topic, I'm aware, but maybe somebody here knows more about this stuff...
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Old April 24, 2021, 03:51 PM   #2
74A95
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How about a link to this magical Russian thingy so we can understand what the heck you're talking about? Thanks.
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Old April 24, 2021, 04:15 PM   #3
Rob228
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https://www.forgottenweapons.com/rus...nt-ammunition/

The burning powder pushes a pistol which pushes the bullet, but all of the gasses are trapped inside of the casing. If I recall correctly, the empties were a bit dangerous because they were containing a significant amount of pressure.
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Old April 24, 2021, 04:58 PM   #4
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Quote:
All this considered, how can a device where the bullet only ever gets an impulse, without any pressure building up in the barrel, drive a bullet through the rifling, overcoming the friction (the "tunnel rat" revolver was smooth bore, but the Russian pistols do have rifling) and still produce muzzle energy to speak of?
The physics are straight forward. A sufficiently hard initial "push" on the bullet will do it, though one does lose the benefit of continued push down the barrel that powder gives.

If I remember right, the QSPR (tunnel rat gun) was a .44 Magnum, and the cases did contain a tiny bleed hole so after firing pressure was vented, but in such a manner as to not sound like a regular gunshot. And yes it was a shot cartridge and the barrel was smoothbore. I don't remember any energy figures on the shot but I'm fairly sure it was less than regular .44 Magnum.

Which means that, though less than the magnum power the case size might have allowed it was still enough to be lethal and sufficient for duty use.

No reason you couldn't make a similar system using bullet and rifled barrel. Using a large enough (and strong enough) case say, .44 Mag size and make it with a captive piston capable of pushing out a bullet to the level of .45acp performance, very quietly.
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Old April 24, 2021, 06:50 PM   #5
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Not sure the experimental .44 was well liked. Impromptu Rats borrowed the LTs .45, which made a heck of a bang in the tunnel.

Others carried .38 snubs they bought on the black market, or were given by other Rats. Some had .22s, like Colt Woodsmen or Hi Standards.

Mangold and Pennycate's Tunnels of Cu Chi is a great book on the subject, available very inexpensively online. Recommended.
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Old April 25, 2021, 11:32 PM   #6
Shadow9mm
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I remember seeing a vid with someone talking about this stuff. I cant remember where. They said it was designed for CQC and was not effective in much larger distances that a small to medium sized room, such as you might encounter in large house. But very effective for the designed use scenarios.
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Old April 28, 2021, 03:08 PM   #7
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If you look at the ballistics quoted in the article, the velocity was quite low (475 fps) and, with a 122 gr bullet, produced roughly the same muzzle energy as a .25 ACP. In order to get this, they had to use a case with nearly the capacity of a standard 7.62x39 rifle cartridge and it had to be used in a gun that was essentially a double derringer. Just looking at it leads me to the impression that in order to work it has to have substantially more case capacity than a conventional cartridge to achieve the same ballistics (both to have room for the piston and to have enough powder to achieve a useful velocity with the piston setup). The design of the cartridge also seems to preclude it's use in any sort of magazine-loading design, self-loading or manually operated. All in all, while interesting, I'd say it's obscure for a reason as the benefit doesn't really seem to be worth all the trouble to me.
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