 Later M4A1, M4A2, and M4A3 models received a larger turret with a high-velocity 76 mm gun from the T23 tank.The first standard-production 76 mm gun-armed Sherman was an M4A1, accepted in January 1944, which first saw combat in July 1944 during Operation Cobra.Variants of the M4 and M4A3 were factory-produced with a 105 mm howitzer and a distinctive rounded mantlet, which surrounded the main gun, on the turret.