SERVICE – Office of Strategic Services and Special Operations Forces
With the increasing importance of intelligence gathering and special operations to be conducted behind enemy lines, a weapon was needed that minimized detection when it was fired. A request for such a weapon was given to the Army by the Office of Strategic Services. The answer to the request was to place a suppressor (silencer) on a firearm, and the M3 submachinegun showed itself to be particularly acceptable to using a suppressor. Western Electric Bell Laboratories designed a suppressor that could simply replace the barrel assembly on an M3 submachinegun. In May 1944, the High Standard Manufacturing Company was contracted to produce 1,000 suppressed barrel assemblies for the M3 submachinegun. By August of that same year the first suppressed M3 barrels were sent to the field.
The suppressor surrounded and extended past the standard barrel of the M3. Modifications to the barrel of the submachinegun included drilling 4 rows of twelve 6.35 mm (1/4 inch) holes (48 holes total) the length of the barrel. The end of the barrel was threaded to fit into an adapter plug. The adapter plug held a 19 cm (7.5 inch) length of 1.37 cm (1 1/5 inch) tubing tightly against the barrel bushing which had been machined to accept it. Surrounding the barrel was a roll of 16-mesh wire screen that filled the space between the barrel and the outside tube.
The adapter plug was threaded to seat the 17.8 cm (7 inch) length of 2.9 cm (1 1/8 inch) diameter tubing that made up the front assembly of the suppressor. Inside the front tube was a stack of 230 30-mesh washers, each with a 12.7 mm (1/2 inch) hole through the center of it. The washer stack was held in place by a threaded muzzle plug, also with a 12.7 mm (1/2 inch) hole through the center.
The suppressor assembly was screwed in place on the front of the M3, in the place of the standard barrel. The suppressor was well received by the operators who used it, both intelligence units and scouts. At a distance of 91 to 182 meters (100 to 200 yards), depending on the environment, the sound of the weapon firing could not be discerned. Even close up 23 meters (25 yards), it was difficult to hear that a weapon had been fired. The sound could be heard, it was described to be like a soft clapping of the hands, but it did not sound like a weapon discharging. Additionally, the added weight and length of the suppressor barrel was found by the users to make the M3 easier to hold on target during a burst.
