Despite the launch of mass production of the M3 medium tank in the summer of 1941, the development of an improved version with a 75 mm gun in a rotating turret was started earlier in winter of the same year. Two prototypes were produced by the autumn of 1941. The military was mostly satisfied with the improved version but also requested some improvements. As a result, the vehicle lost its side doors and the commander's cupola machine gun. On September 5, 1941, the Armaments committee recommended standardizing the vehicle under the Medium Tank M4 designation.
VVSS T412
Wright Continental R-975EC2
SCR 210
T6
75 mm Gun M2
VVSS T482
Wright Continental R-975C4
SCR 506
M4
75 mm Gun M3
75 mm M3 Tank Howitzer
105 mm M4
Characteristics are specified for vehicles with crews trained to 100%.