|Date of first acceptance||April 1942||Total acceptances||5380|
|Manufacturer||Fargo Motor Corporation||Crew||
|Ground pressure, tires||40psi
|37mm Gun M3||M25 or M26 on rear of vehicle||80 rounds||360°
|+15° oto -10°
|Engine||Dodge T-214; 6 cylinder, 4 cycle, in-line gasoline|
|Horsepower||Net: 99@3300rpm||Torque||Net: 184 ft-lb@1400rpm||Fuel capacity||30gal
|Transmission||Selective sliding gear, 4 speeds forward, 1 reverse|
|Brakes||Hydraulic, internal expanding|
|Semi-elliptic leaf spring||2/side|
|Max level road speed||55mph
|Angle of approach||36.5°||Angle of departure||31°|
|Max vertical obstacle||12"
|Min turning diameter||44'
|Max fording depth||35"
|Cruising range||~180mi, roads
The 37mm GMC M6 placed the 37mm gun M3 on the back of a four-wheel drive 3/4-ton truck. The weapon was intended to be fired to the rear, and the only armor on the vehicle was the gun shield. A 5000lb (2300kg) self-recovery winch was at the front of the vehicle. The differences in the gun mounts M25 and M26 included the installation of revised firing controls and a recoil guard for the gunner on the gun mount M26. The vehicle was standardized as the 37mm GMC M4 on 26 December 1941, but in February 1942 the designation was changed to M6 to avoid confusion with the M4 tank. The M6 was an interim design to be used until a fully-armored carriage was designed, and all but 100 of the remaining M6s were converted back to their truck base by November 1943. The M6 was classified as limited standard in September 1943, but not declared obsolete until January 1945.