M3 ‘Grease Gun’, U.S.

M3 ‘Grease Gun’, U.S.

M3 ‘Grease Gun’, U.S.

Type Submachine Gun
Weight 3.696kg
Length, stock extended 74.5cm
Length, stock retracted 57.0cm
Barrel Length 20.32cm
Rifling 4 grooves, RH twist
Cyclic Rate 450 rounds/minute
Caliber .45ACP
In Production 1942-1944
Effective Range 50 meters
Country of Origin United States

Cheap, ugly and efficient, the M3 submachine gun entered U.S. service in December of 1942 and remained in the first-line service until 1960. The original M3 can be distinguished from the later M3A1 by the presence of a bolt-retracting handle. The later M3A1 replaced this feature with a crude but sufficient finger hole in the bolt.

The M3 submachine gun was designed, like the British Sten gun and the German MP40, as an easily manufactured, low cost, sturdy ‘bullet hose.’ It was developed by well-known weapons designers George Hyde and Frederick Sampson, Chief Engineer of General Motors’ Inland Division. Although officially designated M3, it was almost immediately dubbed the ‘Grease Gun’ by the troops who used it.

Constructed mainly of stampings and pressings, with a swagged barrel the M3 was a simple, robust, and reliable weapon. Its rate of fire was deliberately set at a low 450 rounds/minute for greater control and so that the user could trigger single shots as well as sustained bursts. The main weakness of the gun lay in the magazine, which tended to jam unless it was very meticulously maintained. The problem was somewhat alleviated by the issue and use of a plastic dust cap, but the magazine itself was never improved.

As simple as it was to produce, the M3’s designers felt they could do better. In December 1944, General Motors’ Guide Lamp Division, the makers of the M3, came out with the M3A1 (left, click for full-sized image); an even further simplified gun. The entire retracting handle assembly was eliminated. In its place, a crude but useful finger hole in the bolt was used for retracting. The ejection port was made more substantial, the cover spring made stronger, and a bracket was welded at the rear end of the stock. This bracket was used as a loading tool for pushing cartridges into the magazine, a task that was previously a                                                                                              finger-cramping exercise for G.I.s.

In the early part of the Second World War, the infantry board of Fort Benning, Georgia studied the use of silencers on submachine guns. Shortly afterward, the High Standard Manufacturing Company was commissioned to equip 1000 first perforated M3 barrels with mufflers for the Office of Strategic Services (OSS).

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