The T49 57mm Gun Motor Carriage was the second step in a series of designs that led to the M18 76mm Gun Motor Carriage 'Hellcat' and was an upgunned version of the T42 37mm GMC. The T42 was designed by General Motors and had a lower profile than the M10 GMC, which was based on the M4 Sherman tank. Work on the T42 began in December 1941, but it was still at the design stage on 1 April 1942 when the Army decided to move from the 37mm gun to the M1 57mm gun.
On 18 April an order was placed for two pilot T49s. They were to use the M1 57mm gun, keep the Christie suspension (with five road wheels on each side), have a crew of five, with a weight of 12 tons and a top speed of 50mph. Armour was to be rather thin - 7/8in (22mm) on the turret, hull front and sides and 3/8in (9.5mm) on the top and bottom. The T49 carried a hull machine gun.
The first pilot was ready for testing in July 1942. The basic design was good, but at about the same time Army Ground Forces decided that the 57mm gun wasn't powerful enough. The Ordnance Department, and General Bruce, commander of the Tank Destroyer centre, asked GM to complete the second pilot with the M3 75mm gun that was used in the early M4 Sherman tanks. The up-gunned vehicle was given the designation T67.
Engine: 330hp twin Buick engines
Length: 17ft 10.5in
Width: 8ft 9.75in
Height: 75 0.25in
Top Speed: 51mph