The Suppressed OSS M3 Grease Gun with a Trigger Booby Trap

Ian McCollum of Forgotten Weapons is back with another supremely awesome gun for us to check out. This time Ian has his hands on a rare, suppressed World War II M3 Grease Gun issued by the American Office of Strategic Services (OSS). If you’re not familiar with the OSS, it was founded during World War II by “Wild Bill” Donovan and is considered the forerunner to the CIA. They cooked up all kinds of dirty tricks behind enemy lines during the war, directly and in support of resistance movements. Ian also has one of those dirty tricks to show us in the second part of the video.

Quietly Taking the Fight to Hitler

The M3/M3A1 Grease Gun was the American replacement for the iconic Thompson submachine gun during the war. Unlike the Thompson, it was inexpensive and could be mass produced quickly in large numbers, which was a vital necessity during a global war.  The Grease Gun’s lighter weight and compactness attracted the OSS for its operatives in occupied Europe and the resistance fighters they supported. They wanted suppressed guns for clandestine work, which is totally understandable behind Nazi lines.

Suppressed M3 Grease Gun with Bushmaster Booby Trap Forgotten Weapons
Ian McCollum is back with a very cool suppressed Grease Gun built for the OSS in World War II

This particular M3 is one such weapon. It was dropped late in the war to a European resistance fighter with orders to cross the German border and assassinate a Nazi politician. The war ended before he could embark, and the orders were revoked. Turns out that no one asked for the weapons back, so he kept them. My kinda guy. They now belong to a private collector, who allowed Ian to check them out.

Forgotten Weapons Grease Gun suppressor
The High Standard Suppressor easily screwed onto the receiver of any Grease Gun.

The first Grease Guns, so nicknamed because they resemble the mechanic’s tool of the same name, rolled off the production lines in May of 1943. The Maxim Silencer Company soon proposed a suppressed version, and a prototype was built that fall. The suppressors were ultimately made by the High Standard company and production started in early 1944. The first units shipped in August. Ian says it’s unclear how many were used in the field, but they were quite popular, especially since the suppressor’s weight on the front of the gun reduced the felt recoil of an already very controllable submachine gun.

suppressor ported barrel
The suppressor came complete with a ported barrel that was fully interchangeable with a standard M3/M3A1 barrel.

Simple and Effective

The suppressor system is really pretty impressive for the time. It’s fairly simple and its modularity is a big plus. The M3/M3A1 has a barrel that easily screws on and off as part of the disassembly process. The suppressor assembly was built around a new barrel that could simply replace the standard barrel of any M3 or M3A1 in service. Unlike the British STEN gun, there was apparently no need to lighten the bolt or recoil spring for the action to cycle while suppressed. The suppressor assembly shipped as a unit and was matched to the desired gun later. Again, this is different from the STEN, which required an armorer to match the suppressor to a particular bolt and recoil spring.

grease gun suppressor
The barrel was wrapped in wire mesh to trap the gas and release it slowly.

The suppressor uses wire mesh instead of baffles, as did High Standard’s pistol suppressors of the day. It breaks down into two main components, one of which contains the barrel, and another extending past the muzzle. The barrel itself is ported, releasing gas into a wire mesh wrap which traps and slowly releases it. The ports are unnecessary to slow down the .45 ACP cartridge, which is already subsonic. They could, however, be helpful if one of the 9mm conversion kits were used on the gun. The OSS had such kits meant to enable the shooter to use British or captured German ammo if desired.

Forgotten Weapons grease gun suppressor
The ‘muzzle device” was packed with thin wire mesh rings that worked the same way as the barrel wrap. The included guide rod made the rings easier to handle in disassembly.

The “muzzle device” part of the suppressor was packed with thin mesh rings which operated like the barrel wrap, trapping the gas and releasing it slowly. The result was a suppressor that was quieter than the gun’s action as it cycled. Ian found a reference that claimed the suppressor achieved 89 decibels, but he warns us not to take that at face value as there was no reference to how that number was arrived at and there was no standard way of measuring decibels at the time. The assembly contained a guide rod to help keep the thin mesh rings in place when disassembled.

The complete High Standard suppressor assembly for the M3/M3A1 Grease Gun.
The complete High Standard suppressor assembly for the M3/M3A1 Grease Gun.

OSS Dirty Tricks

The OSS had some real Hollywood quality gadgets in its arsenal. The one Ian shows us with the M3 Grease Gun is pretty ingenious. Like the gun, it came from the unnamed European resistance fighter. It’s called a “Bushmaster” and allows the user to set the Grease Gun to fire a full magazine off a trip wire, but such devices were also available with push or time pencil triggers. The latter was chemically released to set off the trigger in a given amount of time.

The Bushmaster trigger paired with the clamp and plunger device allowed an OSS operative to set up a nasty trip wire booby trap.
The Bushmaster trigger paired with the clamp and plunger device allowed an OSS operative to set up a nasty trip wire booby trap.

The Bushmaster screwed onto whatever device was needed by the operative and set it off when tripped. In this case, a plunger was clamped to the trigger guard and activated by the striker from the Bushmaster. The clamp and plunger assembly takes two different thread patterns, one for the OSS triggers and one for the different pattern used by its British counterpart, the Special Operations Executive (SOE).

The striker was held in place by a cotter pin, which was removed to arm the device. When tripped, the Bushmaster’s tension spring drove the striker against the plunger, which depressed the trigger and held it there, firing the whole magazine at whatever tripped the wire. As Ian points out, the operative would have to fix the gun securely for it to work properly.

Suppressed M3 Grease Gun with Bushmaster Booby Trap Forgotten Weapons
When tripped, the striker in the Bushmaster pressed and held the plunger on the trigger until the entire magazine was expended.

It’s pretty damn cool, if you ask me. There are plenty of good books on the OSS and guys like Donovan and his top lieutenant, Allen Dulles, who founded the CIA. My favorite is You’re Stepping on My Cloak and Dagger, the hilarious (but true) account of OSS operative Roger Hall. Anyhow, you should check out Ian’s video to see him break it all down. It’s excellent, as always.

You're Stepping on My Cloak and Dagger is a hilarious book by OSS operative Roger Hall. (Photo Amazon)
You’re Stepping on My Cloak and Dagger is a hilarious book by OSS operative Roger Hall. (Photo Amazon)
William "Bucky" Lawson is a self-described "typical Appalachian-American gun enthusiast". He is a military historian specializing in World War II and has written a few things, as he says, "here and there". A featured contributor for Strategy & Tactics, he likes dogs, range time, and a good cigar - preferably with an Old Fashioned that has an extra orange slice.

Sign Up for Newsletter

Let us know what topics you would be interested:
© 2022 GunMag Warehouse. All Rights Reserved.
Copy link
Powered by Social Snap