 It was a new gun with a breech similar to that of the 75 mm M3 Gun but with a new tube (barrel and cartridge chamber) design to accommodate a new cartridge.It fired the same projectiles as the M7 gun mounted on the 3in Gun Motor Carriage M10 tank destroyer and towed 3-inch Gun M5 anti-tank gun, but from a different cartridge case.The "76-mm" designation was chosen to help keep the supply of ammunition from being confused between the two cannon.