Back in the late 70’s Russia came up with a cool concept. A silent cartridge. You can see the cut away above and below. The long cylinder is the projectile and the red piece under it is the piston. When the primer is struck it ignites the powder like a conventional cartridge. The combustion pushes the piston and that pushes to projectile out. The piston is wide so it cannot get past the neck at the top. This seals the cartridge and the gas cannot escape. This results in very little noise coming from the combustion. It has been reported to have a noise level of only 110 db, similar to a suppressed sub sonic .22lr.


There are three weapons that use this cartridge. The PSS semi auto pistol, the OTs-38 revolver and the NRS knife.


  • B-Sabre

    That looks like about the least aerodynamic projectile possible.

    • ExMachina1

      Guessing this is meant for very “close” work

      • Gary Kirk

        Very “wet” work…

    • AlDeLarge

      More than a few revolver and lever gun rounds have flat noses with little ogive. Wadcutters are completely flat with no ogive at all.

  • Younggun

    Interesting concept. The obvious problem that comes instantly to mind would be case capacity for powder. In other words, you might be getting the sound of a suppressed .22, but are you getting any substantial energy out of it?

    • The late Charles Cutshaw claimed that he saw the SP4’s projectile pierce a Level II vest at 25 meters during testing.

      • iksnilol

        Wouldn’t surprise me if it was some improved penetrator in those bullets.

        • The projectile is basically a steel rod with a copper driving band.

    • int19h

      It’s not just the case capacity, but also, as soon as piston reaches the end of the case, there’s no further force applied to the bullet. Whereas in a conventional system, there’s some force for as long as there’s higher pressure behind it, and so long as it’s higher than friction, the bullet keeps accelerating. So, yes, energy-wise, this isn’t all that impressive. But it makes a much bigger hole than .22…

      • Younggun

        So how much energy are we talking then? A bigger hole doesn’t really speak to me unless there is some horsepower behind that, otherwise we are talking about puncture wounds. All that in a cartridge size that is going to be longer than 9mm and maybe longer than most 10mm which makes it unwieldy in a handgun grip. So you’d need a handgun with a larger grip than a 10mm to do the damage of a pointy stick? Maybe I am missing something in terms of the type of energy that can be generated here and if so I am happy to hear someone with some experience with this concept or something similar.

        • int19h

          According to Modern Firearms:

          9,3 g / 143 grain
          200 m/s / 655 fps

          • Giolli Joker

            Modern Firearms also lists the data on the newer version (SP-16) running at about 300 m/s. I guess we are in the range of a 9 Luger with 147 grs load, then.

        • Tom

          I believe that the main use of such ammunition was for assassinations at close quarters hence ‘power’ was not too big a concern. Also such ammunition can be used in revolvers which cannot be ‘easily’ suppressed. Using a revolver one does not need to worry about policing brass and when the authorities recover the slug they have something which looks far more like a rifle round than a pistol round which throws them off a bit – a similar concept was used in a Sherlock Holmes novel all be it reveresed a .455 or .450 calibre pistol round was fired from a specially made air rifle so that Holmes and co initially though the shooter must have been in close proximity to the victim.

          So what you have is a near silent round fired from a small pistol (no added length from a suppressor so its quick to bring to aim and conceal once the deed is done) which does not eject brass and a projectile which when recovered suggest a subsonic rifle round from range rather than a handgun at close range. Basically a near perfect assassination weapon (not as good as a Glock 7 of course but those things are made from porcelain and do not set off metal detectors but they cost more than a police chiefs monthly salary!) as its quiet and the only evidence it leaves is likely to confuse the authorities and mislead them.

          Bare in mind that such weapons were developed in secret and its only post Cold War that we know about them. Who knows how many enemies of the USSR may have met their end from such weapons leaving those who had to investigate scratching their heads.

          • Younggun

            Interesting context. Makes a lot more sense now as a very specific weapon platform.

          • Clarence Bodiker

            So your saying this is a Red October bullet with a nearly silent propulsion system.๐Ÿ‘

          • Phillip Cooper

            “albeit”… not “all be it” for future reference…

          • LilWolfy

            They had one with a 63mm length that was found in El Salvador in the 1980s, an over-under break open action basically like a large Derringer, meant for assassinations by UC operatives pushing the communist goals of subversion.

          • actually during the cold war they were known. the US and likely the British and others had developed/were using them.

            The beauty of these is that you can use things that look say a tire gauge or pen to deliver the bullet and have it be virtually noiseless.

    • Giolli Joker

      They seemed to do their job… .38 Special ballistics roughly.
      The new versions are hotter.

      • noob

        I’m told that is part of the appeal – You pop a sentry at close range with one of these things, and he ends up with either an ak bullet or a weird deformed metal shank in him with no powder stippling and wounds consistent of being shot from 200m or more. On finding the body, the search party goes out to a likely position 200m away from you and you continue on doing whatever guys in blue and white striped shirts do for funsies.

  • Charles Adams

    The US Army had developed the same thing back in the 60’s, designed to be fired from a modified S&W MD 29. The stated purpose was for “tunnel rats” in Vietnam.

    • Here is the ACTIV report on the QSPR’s use in Vietnam.

      And here is AAIโ€™s project report on the QSPR.

    • Joshua

      As I understand it, it wasn’t commonly used in that role for some reason, it saw some use with ambushes though.

    • Raoul O’Shaugnessy

      Indeed. The captive piston ammo was, basically, .44 caliber shotshells loaded with buckshot. The captive piston cartridges worked well, but didn’t have nearly the energy that was hoped for. Additionally, it was tricky business machining the cases to hold the pressure without blowing the primers out the back of the case. Nothing much ever came of the guns, but some of the ammo, interestingly, did turn up in a bank robbery in San Francisco during the war years. There’s a bit about the Tunnel Weapon project guns in Supica’s S&W book.

      • there was a limited number of the revolvers but from what I heard it worked well. thing is intergral silenced 22s based on the Ruger could do the same job and came out about the same thing.

  • While the Russian captive piston silent cartridges and firearms are fairly well known, there has been very little written about their US counterparts outside the efforts of AAI, Inc. So here’s a data dump on the Silent Weapon System – Alpha and related captive piston piston cartridges.

    Here is the patent for one of the earliest US captive piston cartridges, the Cal. .30 XM76. The XM76 was intended for use in legacy .30-06 firearms. However, the lackluster ballistics (~.32 ACP / .32 S&W Long level) combined with the noise of manually operating the host firearm left potential users underwhelmed. The proposed equivalent in 7.62mm NATO, the XM115, was dropped quickly.

    This led to the development of larger captive piston cartridges and a dedicated repeating firearm to use them – the Silent Weapon System – Alpha. Here are a few publicly available reports mentioning the project.

    “Silent Weapon System Cartridge Design and Development. Phase I: Design”

    “A Source of Small Arm Muzzle Noise”

    โ€œDevelopment of a Silent Weapon System”

    I think the following patent may illustrate a magazine intended for the Silent Weapon System – Alpha prototypes on display at the Rock Island Arsenal Museum. These are Items 5810-5813 in the photo below. Note that there is no chamber. They really didn’t need one, given the thick steel cases of the Alpha-series cartridges. After the Alpha1 series, they didn’t even bother adding an extraction groove to the later variants of the Alpha cartridges.

    • demophilus

      Thanks for the links.

      IIRC, the USN’s Mk.1 Underwater Defense Gun used captive piston rounds, as well. I vaguely remember reading that captive piston devices are quite common in other military applications, like jettison systems, so the Navy had prior art to work with.

      IIRC, the Navy also tested silent 12 ga. shells with a reversible metal cup holding the shot; the powder charge made it invert. The shells allegedly didn’t prove out, as you still had to manually cycle the action.

      Later KAC converted a Ruger Redhawk to fire a suppressed case telescoped round, but UIM, it wasn’t captive piston; it had some kind of gas seal around a smaller caliber bullet driven directly by propellant.

      I wonder how many more of these things are out there. The Mk. 1 UDG only came to light a few years ago.

      • Here are AAI’s patents for the Mk 1 Mod 0 UDG and its ammunition.

        Here are the patents for the expanding diaphragm schemes used by AAI for their silent shotshells and 40mm grenades, both 40x46mm and DBCATA.

        The ammunition for the KAC suppressed revolvers didn’t use a captive
        piston, but a captive sabot. The large caliber sabot stopped against
        the forcing cone of the small caliber barrel to seal the cylinder gap.
        The propellant gases were then left to flow into the suppressor.

        In articles that I’ve seen, the project was credited to Reed Knight and
        John Anderson. However, the cartridge concept is derived from an earlier
        design by Charles R. (Bob) Olsen. He saw it as the basis for a high
        velocity revolver cartridge without the need to use a bottlenecked case
        with its setback problems. He called it the Invicta. The models he
        showed to the shooting press back in the early/mid-80s were built on Dan
        Wesson revolvers. I suspect that no one wanted to market it due to the
        possibility that some idiot would slip a standard cartridge into the
        cylinder and try to shoot it out of the smaller diameter bore.

        These are Olsen’s patents:

        • demophilus

          Thanks, guy. I’ll have to take a look at those.

          I’ve read your posts here and other boards, and have come to respect your virtually encyclopedic knowledge of firearms. Here’s a question that’s stumped me for a while; it’s not a challenge. Given the subject, I’d understand any reticence you may have.

          DTIC’s 2007 Chinn award went to an engineer who worked on a “disposable 21 shot electrically fired pistol”. Any idea what that’s about? I’ve never read anything about it anywhere else. If it isn’t a darker shade of black, I’d like to know more.

          • electrically fired pistols have been around for a while. Remington had a rifle that was sold on the commercial market that was electrically fired back in the early 00s. Usually electrically fired guns are meant for underwater usage. Advantages to electric primers are no lock time and less trigger pull plus maybe less recoil since you don’t have the primer explosion.

            it is possible the Chinese one is one meant for underwater usage by special ops like the HK one which looks like an electric razor but you have to change the head after firing the four darts it has to reload.

          • I have to admit that I don’t remember seeing anything about that pistol either. Perhaps it was merely a scaled-down, handheld version of his CABWS (Counter-Ambush Barrage Weapon System) design? The latter was basically an electrically-fired millatreuse chambered in .22 LR.

  • CommonSense23

    The US military had the same concept developed for both pistol and shotguns in the 60s.

    • PK

      1962. Rifles, too. Interesting use of DU, actually! Some of those designs were really out there!

  • Patriot Gunner

    Well that’s one way of getting a quiet firearm without a silencer…Take that NFA!

    Oh wait a min we just received a new interpretation letter from the ATF stating that these are integrally suppressed short barreled rifle AOW’s…dang

    • Giolli Joker

      Actually word out there is that each of these cartridges would carry a 200$ stamp…

      • iksnilol

        They should make spring loaded ammo. Like a (hella) powerful spring that’s cocked and with a regular projectile in it. Then just make a firing pin hit a “primer” to unleash the spring. No gas at all should be even quieter.

        • AD

          Have you ever heard of the Brocock Air Cartridge (BAC or TAC cartridge system)? It used compressed gas but otherwise was similar to what you described. Sadly it was killed in the UK by media sensationalism and outright lies, but I’ve heard they are still legal and in use in some other countries in Europe like Spain.

          • iksnilol

            I’ve heard about Brococks. Should’a done revolutionized airguns (which I’m taking an interest in due to cheap ammo and much more shooting space). Of course UK govt killed it ๐Ÿ™

            They’re probably legal most places outside the UK. But doesn’t do a lot of good if they aren’t manufactured anymore. So I’mma settle for a Benjamin 397 as a self contained airgun for hunting rabbit or sometihng (I can get heavy ammo for it, and intend to see what can be done to increase velocity some.) Hypotethical hunting of rabbit of course, since airgun hunting is illegal in Norway. I would’a gotten the .22 version but the ammo is heavier, more expensive and in Norway I’d need to register it with the police (airguns over 4.5mm have to be registered). Will get a PCP as well, though.

        • Giolli Joker

          That’s the concept of a ballistic knife that is actually NFA item in the US.

          • iksnilol

            Yeh, but like hella tiny so that you can load them in a .44 or .357 :p

            Also, there are different ballistic knives. Those with built in gun and those that shoot the blade itself :p. So I did misread your comment and thought of a gun that shoots smalker guns that shoot bullets ๐Ÿ˜ฎ

          • Giolli Joker

            I referred to the one shooting the blade. IIRC it is a felony in the US to manufacture a spring loaded ballistic knife, it is not to manufacture one that shoots the blade by means of a blank cartridge (hence a monstrosity from RJ firearms in one episode of Sons of Guns).

          • iksnilol

            Oooh, I remember that one. Hey, launching via blank cartridge is safer, since people can hear it ๐Ÿ˜€

        • Blake

          high-powered airguns are pretty cool

          • iksnilol

            Nah, they get hot.

        • hw97karbine

          You can use compressed air instead of a spring.

  • Guns from scrap

    How a PSS silent pistol works

    World of Guns Disassembly game is free on steam

  • Tassiebush

    Mate this with metal storm tech in a gun umbrella and lace them with poison so you have a captive piston cartridge gun that fires poisoned captive pistons (which probably rupture on impact. That’d have to get on forgotten weapons!
    I’m going to see if I can patent that alongside my hydrogen and hot air balloon zeplin hybrid!

    • Does the name Georgi Markov do anything to you?

      • Tassiebush

        Well it makes me feel like my idea is a bit distasteful! ๐Ÿ˜‰

  • Maxim Popenker

    The story of the Russian captive piston ammo is much older than mentioned in this article
    Some time ago i did a guest post at which goes into some details on the subject:

  • jerry young

    I wonder with all the pressure contained in the case and the piston being jammed at the neck of the case how prone this would be for the case to become jammed in the chamber, how many shots could a normal gun take like this before the chamber ruptures? more than likely the gun would have to be specially designed around the ammo adding even more expense, I’ve seen normal cases where someone would hand load what they call hot loads and the primers blew out or the cases split, it seems this would be a common problem with this design and very expensive ammo to produce

    • mechamaster

      Yeah, the gun is designed around the cartridge.
      It’s commonly something like short and compact multibarrel derringer-type and revolver, or 1-shot type. ( the exception is PSS is the semi-auto pistol that utilized SP-4 type cartridge and NRS-single shot knife ). So the squib load is minimalized by the design.
      And the pressure is limited because of the small-amount of gunpowder inside

      And of course, because it’s tailored for “special forces-tool”, the premium price is not a problem.

      • They had various types of sp ammo. Some were designed for the gun they were used in others could be used in any handgun. One model was a three shot that looked like a cig case. Apparently you could fire it in a crowd and no one would know that a person had been shot.

        It is also used by certain police units. Last I heard in some areas they were having trouble getting it due to shortages.

        The issue with the pss and other semi autos is that the casings are very distinct and can be readily identified by any knowledgeable person.
        Hence a gun that you manually extract the casings tends to be more favorable for most wetwork.

  • Michael Morelan

    A very good read. Thanks for posting.

  • jcitizen

    Reminds me of that silent grenade launcher the Russians made, that had a separate chamber to load a special launcher round in, and pushed the grenade out by a sealed piston activated by the launch round. If I remember correctly, it had decent range.

    • Leveller

      If it was called the “Gull”?/! Range was ~1,200-meters…

      • jcitizen

        Gull may be an airsoft description – I believe it was called the BS-1 Tishina

  • maodeedee

    More information would be nice, like, how much does the projectile weigh, and does it engage the rifling and what velocity is it capable of?

    • it will kill at a distance of 60 feet but is meant for more close up. Also the tonal noise is such that you could fire this off in a crowd and nobody would know a gun had been fired. It is about 300-500 fps from what I remember. It is a gun meant for wetwork after all.

  • Secundius

    Actually is Predates the Russian by almost 90-years, Samuel Marsh of Nottingham, England invented the “Piston Cartridge” in 1879 for the Mining Industry. In the application of Shale Gas Mining, but limited by the Technology of the time to a Maximum Applied Force of ~10,000psi…