The kit uses all new tooling with the exception of the suspension parts as they are from the M4A3E8 Sherman "Easy Eight" model kit. The M40 was a significant step in U.S. Army artillery mechanization, pairing the M1 155mm gun with the proven M4 Sherman chassis. Armour was light given its intended use as a long range weapon (they were effective up to 23.5km) away from the front line, while the layout was changed from the M4 to allow a big fighting compartment at the rear to accommodate the big gun. It was fitted with smooth horizontal volute spring suspension (HVSS). Over 400 were produced before the end of WWII; although they never fought in the conflict, one example of their T83 prototype did. The M40 served in the Korean War, and was eventually replaced by the M53.
Manufactured toward the final stages of WWII, the M40 self-propelled gun design employed a combination of proven M4 Sherman chassis components and the powerful 155mm "Long Tom" gun. It was a boon for the 8-man U.S. crews that deployed it, not least because of the serious mobility upgrade it offered over its towed artillery piece predecessors, and an impressive range of 23.5 kilometers using explosive rounds; stability when firing was provided by a large rear spade. A 460hp air cooled engine enabled a top speed of 38km/h. Production began in February 1945, and while it was officially adopted in May 1945 none of the 418 manufactured by the end of WWII saw action. Instead, this powerful SPG was deployed in the Korean War, in which it provided long range bombardments of enemy positions.