M4 Tractor

The M4 was intended to tow three different artillery pieces: the 155mm gun, the 8in (203mm) howitzer and the 90mm anti-aircraft gun. The M4 HST also was designed to carry ammunition for these weapons in a box at the rear of the chassis. The ammunition box for the 155mm gun and 8in howitzer were the same externally, but had slightly different internal arrangements due to the size of the ammunition. The type for the 90mm anti-aircraft gun was slightly different due to the stowage method and had side-opening doors for access to the ammunition. Production of the M4 began in 1943 and a total of 5,552 were built through 1945 when the slightly improved M4A1 appeared. Towards the end of production, it was decided to use the M4 to support the new M40 155mm GMC and M43 8in HMC as an ammunition carrier in lieu of the M30 previously used with the M12 155mm GMC. These carried additional ammunition in the rear of the crew compartment in lieu of the crew seats and were designated as M4C. There were a number of production changes on the M4 from 1943 to 1945 including a revision of the openings on the rear of the hull for the winch, deletion of ammunition box vents, and the addition of a front mounted emplacement pintle on later production tractors.