 The first Sherman variant to be armed with the 105 mm howitzer was the M4, first accepted in February 1944.From May to July 1944, the Army accepted a limited run of 254 M4A3E2 "Jumbo" Shermans, which had very thick hull armor and the 75 mm gun in a new, better- protected T23-style turret, in order to assault fortifications.The M4A3 model was the first to be factory-produced with the horizontal volute spring suspension (HVSS) system with wider tracks to distribute weight, beginning in August 1944.