The T52 Multiple Gun Motor Carriage was a failed design for a self propelled anti-aircraft vehicle armed with one 40mm Bofors gun and two machine guns.
The T52 was the result of a proposal from the Firestone Tire & Rubber Company that happened to match a set of requirements that was developed at a US Army conference in May 1942. The Firestone design was for a ball type turret (rather resembling a barrel), with a single 40mm Bofors gun mounted in the centre and two .50in machine guns mounted on the ends of the barrel. The turret carried a crew of two - the gunner on the right had to aim and fire the gun and reload the right-hand machine gun, while the loader on the left had to load the 40mm gun and the left-hand machine gun and set the range indicator.
The Artillery and Automotive Subcommittee of the Army recommended that the Firestone mount should be tested out on two pilot vehicles. Ordnance approved, and on 30 July 1942 the mount was given the designation Combination Gun Mount T62 and the vehicle the Multiple Gun Motor Carriage T52.
Firestone completed the first turret in October 1942. This was then mounted on the chassis of an M4 Medium Tank, replacing the normal 75mm turret. The first pilot went to the Aberdeen Proving Ground in March 1943, and tests were carried out for the rest of 1943.
The T52 didn't impress in the tests. The turret was too cramped, and the two crewmen overworked. The machine guns were too close to the turret traversing mechanism, and empty shell cases could jam the turret. The turret and guns didn’t move quick enough to keep up with fast moving low flying aircraft. Finally the vehicle only varied 64 40mm rounds, not even enough for one minute of firing at a normal rate.
In October 1944 the Ordnance Department recommended cancelling the project (presumably some time after work actually stopped), and the project was officially cancelled in November 1944