M4 (76mm) Sherman Medium Tank 1943–65

In view of the strong recommendation of General Devers to accelerate the development of the 76mm gun for the M4 tank, Ordnance continued the effort by mounting the weapon on a larger turret. To simplify development, Ordnance decided to adapt the turret of the new T23 medium tank pilot to the M4 tank under the designation M4E6. Two pilots of the M4E6 were authorized on June 17, 1943. They were built by Chrysler’s Detroit plant and delivered in July 1943. The trials were so successful that on August 17, 1943, the Armored Board recommended the M4E6 for production. This went up the chain of command to Headquarters, Armor Command, which on August 21, 1943 recommended that 1000 M4 tanks be procured. The letter to the Army Ground Forces (AGF) also noted that “As soon as the tank has been proven on the battlefield, it is recommended that we go to one hundred percent replacement of the M4 with 76mm gun.”
This remark sparked a controversy. General Devers, after repeated clashes with General Lesley McNair, the head of AGF, was booted upstairs, departing Fort Knox in May 1943 to take over command of the European Theater of Operations (ETO). Devers was replaced by General Alvan Gillem, an infantry officer. Gillem’s first action was to pay a visit to tank units in North Africa and Sicily to determine future requirements. He came back convinced that greater attention had to be paid to tank–infantry cooperation. On his return, Gillem stepped into the dispute over the August 21 letter that had been penned by his subordinates during his absence. He was troubled by the suggestion that production shift to the 76mm gun, as it was less suitable for infantry-fire support against unarmored targets than was the older 75mm gun. On September 1, 1943, Gillem sent a second letter to AGF clarifying the Armored Force’s requirements. He noted that:

‘The 76mm Gun M1 as a tank weapon has only one superior characteristic to the 75mm Tank Gun M3 … armored penetrating power. The 76mm gun will penetrate on average one inch more armor than the 75mm tank gun M3 at the same range. The high explosive pitching power of the 76mm gun is inferior to that of the 75mm gun. The 76mm HE shell weighs 12.37lbs and has a charge of .86lbs explosive. The 75mm shell weighs 14.6lbs and has a charge of 1.47lbs of explosive. The exterior ballistics generally of the 76mm gun are less satisfactory for a general purpose medium tank weapon than the 75mm gun. The 76mm gun has an extremely heavy muzzle blast, such that the rate of fire when the ground is dry is controlled by the muzzle blast dust cloud. Under many conditions this dust cloud does not clear for some eight to thirty seconds. The presence of this heavy muzzle blast makes sensing the round extremely difficult for the tank commander and gunner.’