Suppressed OSS M3 Grease Gun and Bushmaster Booby Trap Trigger

Today, we have a chance to take a look at a suppressed M3 “Grease Gun”, as purchased and issued by the Office of Strategic Services (the OSS; predecessor to the CIA). Thanks to its readily removable barrel, the M3 (and M3A1) submachine gun was an easy gun to adapt to use with a suppressor (or as it was called at the time, a silencer). During World War 2, such a unit was developed for clandestine use by OSS and British SOE agents in occupied Europe, and they would see use for many decades in all manner of conflicts.

The suppressor itself is quite different than modern designs, being a two-part device using tight wire mesh instead of baffles. The barrel itself is heavily perforated, and extends only through the large diameter section of the suppressor. Around it is wrapped a large roll of wire mesh, which acts as an expansion chamber to slow down the exit of gas from the muzzle. The smaller front section of the unit is filled with small discs of the same wire mesh, similar to wipes but made of mesh.

Allegedly, the suppressor was effective enough to reduce the noise of the gunshots below the level of the action cycling, which is all that one can reasonable want from a suppressor. This particular example has an excellent provenance, having been provided by OSS to a European resistance fighter for a specific mission right at the end of WW2.

In addition, we also have a piece of the OSS sneaky tricks catalog to see. Specifically, a “Bushmaster” remote trigger mechanism to allow the M3 (silenced or otherwise) to be made into an autonomous booby trap in conjunction with a time delay, tripwire, or other triggering device.

Many thanks to the anonymous collector who let me take a look at this piece and bring you a video on it!


  1. There was a Red Chinese copy of the M3 in 9 x 19mm in the Fifties that was a dedicated suppressed weapon with a duplicate of that suppressor. They substituted a second roll of wire screening in the forward section for all those little washers. It seemed to work about as well.



    • “in the Fifties”
      With introduction of assault rifle, sub-machine gun role dwindled, however as most automatic pistol cartridges’ bullets travel slower than rifle/intermediate, it is easier to slower them under sonic speed (~300 m/s), thus removing sonic boom effect, thus new niche for sub-machine guns appeared: suppressed weapons.
      So far I know, after adoption of avtomat Soviet Union never adopted suppressed sub-machine gun, nearest match is probably 6P13
      which is machine pistol

      • During Great Patriotic War, silenced versions of PPD and PPSh were tested (ППД-Брамит and ППШ-Брамит), 1st photo from top here
        shows ППШ-Брамит, it used unique 7,62×25 cartridge – 7,62×25 case with “Л” bullet from 7,62x54R (9,5…9,7g) and has muzzle velocity 250 m/s. It was considered impossible to make effective sub-sonic 7,62×25 with usage of standard bullet. Due to bigger overall length, new (thicker) disk magazine was used. ППД-Брамит mass was 6,4 kg (normal PPD – 5,4 kg), it proved to be no worse in accuracy in comparison to normal 7,62×25. Penetration was bit lower at close distance, but equal at 300 m. It proved to be reasonably reliable (1-2% jam rate in unfriendly environment). It was not adopted as it requires special cartridge, deep modification of sub-machine gun and Red Army already had suppressor for rifles and DP machine gun.

  2. Thank you Ian, wow that is a cool piece of history! I wonder if the size of the mesh was large enough that it matched the wavelength of the sound. More likely just as explained…just a place for the expanding gas to disperse its energy.
    I remember reading somewhere that if you cut holes in a metal plate where to holes match the wavelength of the sound that wavelength’s energy is partially absorbed by the metal. Anyhow that’s all something I read about a few years ago about sound dampening for music studios.

  3. The problem with screen mesh washers is that after a few rounds loose wires begin to migrate into the path of the bullet and they drag more wires out of the baffles until the whole thing becomes a mess of meshing.

    As for the vented barrel, that would be more efficient had they used less vent holes and left a inch or two of solid bore at the muzzle to act as a gas seal, actively forcing more gas into the expansion chamber packing.

    Had they designed it that way they might not have needed the end baffles.

    • And it’s older than steam. Trip-fired booby-trap shotguns and blunderbusses were around since before the rise of popular nationalism. Those traps were meant to punish poachers and burglars by riddling them with buckshot. Worse than booby-trap guns would be conventional fragmentation grenades with zero-time fuses (left as schmuck-bait by retreating Germans) or Japanese grenades with percussion-activated fuses (if the Type 97 grenade was placed under a floor board with the safety pin removed, the first Marine to stomp on the plank above the grenade would get blown sky high).

      Did I mess up?

      • No, but you forgot the single most common use. In cemeteries, to dissuade (or just kill) “resurrectionists” who stole bodies to sell to medical schools for dissection.

        While technically illegal (and proscribed by the church in England and elsewhere), this was “winked at” as long as the bodies weren’t those of anybody “of quality”. Which meant that medical students tended to look at a lot of “ginny” kidneys and cirrhotic livers.

        Burke and Hare in Edinburgh (1827-28)were the most (in)famous, not so much for selling dead bodies to Dr. Knox but because the bodies weren’t necessarily dead when B&H Ltd. “took custody” of them. About 18 altogether weren’t, in fact.

        To convince their ilk to leave the bodies of the dear departed alone, a lot of cemeteries had trap guns rigged to blow away anybody who came in at night, regardless. One nasty trick was burying a loaded and cocked firelighter pistol with the corpse- with its muzzle stuck in a small keg of black powder, and its trigger wired to the coffin lid. Putting a pound or so of nails on top of the powder in the keg was popular, too. Sort of a primitive Claymore that fired up and out when set off.

        One typical “resurrectionist” trick was to send a young woman dressed in mourning into the cemetery about dusk, to unhook the tripwires from the trap guns’ triggers. Some cemeteries had “groundskeepers” who were tasked with reconnecting the tripwires after the young lady left…

        Actually, it was simpler, but more expensive, to just bribe the undertaker to put some bags of dirt in the coffin and hand over the stiff. B&H were too cheap to do that- unfortunately for them.

        Trap guns still show up now and then. Winant mentions a Winchester M’92 found wired up in a tree, its stock and forearm rotted away, and hammer down on a fired round. Since it was near the door of a gold miner’s cabin in the Yukon, it may have been set off by a claim-jumper… or by the miner himself coming back after a night of too much imbibing.

        Sorry, no skeleton found in front of the door. (Cue first season “Twilight Zone” end title theme….)



  4. Rather than leaving your PDW as a booby trap for pursuers (unless you had a spare) imagine what these guys would have done with a Claymore.

    I’m sure someone here knows when they were invented, but I’ve never seen any WWII or Korean War stories using them, so I’d guess they came about in the 50s? Certainly seems like something the SOE dirty tricks boys could have conceived.

  5. The M3 greasegun was also issued to heavy equipment operators in Korea.
    A 45 caliber was often suppressed to make use of the subsonic speed of the 45 as opposed to the supersonic 9mm. The US didn’t use 9mm before the 1980s.

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