Know your weapon: The M3 'Grease Gun'


Go grease lightning

When the USA was plunged into the Second World War in 1941 it found itself ill prepared for a full-scale war. Facing shortages both in its existing arsenals and manufacturing capacity, the Americans were impressed by the effectiveness of the German MP 38 and MP 40 submachine guns and the British Sten gun. In response, they sought to create a rapid-fire weapon that could be cheaply mass-produced by American industrial manufacturing processes. 

The task for designing this weapon fell to General Motors, with two individuals in charge of its creation. The first was George Hyde, who was given the task of designing the weapon. A skilled engineer, Hyde – born Georg Johann Heid – was a German immigrant who had moved to America in 1926 and had become an American citizen in 1932. The second was Frederick Sampson, General Motor’s Inland Division’s chief engineer, who was responsible for organizing tooling for production. 

An initial prototype weapon called the T15 was produced, later being replaced in 1942 with the T20, which removed its predecessor’s selective fire function and came with a kit with which to convert the weapon’s original .45 caliber to 9mm Parabellum. 

The T20 was formally approved by U.S. Army ordinance in December 1942 as the U.S. Submachine Gun, Caliber .45, M3. General Motors had the gun manufactured at the Guide Lamp Company in Anderson, Indianna. Purchased by General Motors in 1928, the Guide Lamp company originally made electric lights for motor vehicles, and as a result had extensive experience of pressing and stamping metal components. This made the company an ideal place to manufacture the M3, whose main body was constructed of two sheet-metal pressings welded together. 

Only 900 guns had passed inspection by 31 July 1943, but, by the end of the year, 85,130 had been accepted. Production in 1944 amounted to 343,372, and 178,192 M3 submachine guns were delivered in 1945. The weapon received an upgrade in the form of the M3A1, of which 15,469 were completed by August 1945, though none ever saw combat in the Second World War. The M3A1 would, however, later see service in Korea and Vietnam.

The M3 proved popular with paratroopers, armoured-vehicle crewmen and reconnaissance units, the compact frame and high rate of fire making it ideal for close quarter fighting. Amongst soldiers it soon became known as the ‘Grease Gun’, although it also briefly enjoyed the nickname of ‘Cake Decorator’. Reception amongst troopers was mixed, with some regretting having to relinquish their sturdy M1 Garands, whilst others soon came to appreciate the value of a rapid-fire weapon in close-range engagements. The first combat use of the Grease Gun was reportedly on D-Day by the US Rangers and the 82ndand 101stAirborne Divisions.