The M41 HMC (unofficially known as the Gorilla) was a self-propelled howitzer which mated the relatively new M1 155-mm howitzer with the chassis of a lighter tank compared to the M12/M40. It was originally intended to use the M5 chassis although this was soon changed to the newer M24. Although smaller and lighter, the M41 was broadly similar to the M12 in having an open top compartment for the gun crew and no defensive armament. However, it benefitted from higher speed to both the M12 and M40 as well as a reduced size crew of just five. In terms of armament, the range of the M1 howitzer was inferior to both the M1918 and the 'Long Tom' field guns used on its similar caliber counterparts, but it compensated by having a higher rate of fire. The M41 was introduced in June 1945 but came too late to see action in World War II. However, it was employed with considerable success during the Korean War. A small number of M41s were adopted by the French Army and a few captured units were known to have been employed by China.

The initial prototype T64 was based on the chassis of the M5A1 but only one was built before a second prototype, known as the T64E1, was designed around the newer M24. It entered service as the 155mm Howitzer Motor Carriage M41 in mid-1945 with no other variants produced.