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M3A1 (Grease Gun) Suppressed

Submachine Gun (SMG)

The suppressed M3A1 was a wartime OSS attempt at a special-use M3A1 Grease Gun submachine gun.
Authored By: Staff Writer | Edited: 12/15/2017
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Year: 1944
Manufacturer(s): High Standard Firearms Company - USA
Roles: Clandestine Operations; Close Quarters Battle (CQB)/Personal Security;
Action: Blowback; Open Bolt
Caliber(s): .45 ACP
Sights: Iron Front and Rear
Overall Length: 762 mm (30.00 in)
Barrel Length: 203 mm (7.99 in)
Weight (Unloaded): 8.16 lb (3.70 kg)
Muzzle Velocity: 900 feet-per-second (274 meters-per-second)
Rate-of-Fire: 450 rounds-per-minute
Effective Range: 250 ft (76 m; 83 yd)
Operators: United States
Designed in 1942 with serial production beginning in 1943, the original M3/M3A1 "Grease Gun" submachine gun (SMG) series was procured at the unbelievably low price of $20 per unit in 1943 dollars. The weapon was commissioned from the outset as a budget-conscious, mass-production effort to supplant the more complex and expensive (though still excellent) M1 Thompson SMG series. The Grease Gun was produced to the tune of some 700,000 examples over its service life and managed an active existence extending into the 1990s. It was eventually used throughout the world and across several notable conflicts proving the design sound and something of a market success. The M3 eventually was slightly improved through the M3A1 initiative and chambered for both the American .45 ACP and German 9x19mm Parabellum pistol cartridges, these firing through a blowback, open-bolt action (most production was of the .45 ACP form however). The weapon began appearing in useful numbers from late-1944 into 1945 though saw more widespread use only after the war.

The "Grease Gun" name was derived from the weapon's appearance to a mechanic's grease gun of the period. The original weapon was designed by George Hyde of General Motor's Inland Division with production handled by General Motor's Guide Lamp Division of Indiana.

During the war, the Office of Strategic Services - forerunner to the Central Intelligence Agency of today - entertained the thought of a suppressed version of the weapon. This revision retained the basic form and function of the reworked M3A1 while adding an integral suppressed barrel to the design. The barrels were drilled in specific areas for dispelling propellant gasses and attached to the receiver via specially-designed nuts. Design of the suppressor was attributed to Bell Laboratories at the request of the OSS while barrels were manufactured by Guide Lamp Division with final assembly by the High Standard Firearms Company.

The weapon was not truly a "silent" weapon for it still managed the standard, low-velocity .45 ACP cartridge - inherently subsonic but still producing a telltale sound. The suppressor aided some in retarding the operator's sound profile but the combination was not efficient. The remainder of the gun was largely unchanged and included the standalone pistol grip, collapsing twin-strut wire buttstock, tubular receiver and 30-round straight box detachable magazine which doubled as the forward grip. .

The OSS commissioned for some 1,000 suppressed M3A1s which certainly limited their overall reach in World War 2. Their suppression qualities proved poorer than the excellently-suppressed competing British STEN submachine guns - some 20% more audible than the British design.

Variants / Models

• M3 - Base series designation; initial production model.
• M3A1 - Improved M3 submachine gun
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