M6 Heavy Tank

The US Army Ordnance Corps initiated development of the Heavy Tank T1 in June 1940 following recommendations from the Chief of Infantry. The project was prompted by the successful employment of armored units in Europe and a perceived requirement for a heavy breakthrough vehicle. Baldwin Locomotive Works received a production contract in August 1940, and the first prototype was delivered in December 1941. During 1941 and 1942, developers produced three prototypes to test different transmission systems and hull construction methods, including cast and welded designs. The US Army standardized the cast-hull version as the M6 and the welded-hull version as the M6A1 in May 1942.

The M6 featured a single three-man turret equipped with a vertically stabilized 3-inch M7 gun and a coaxial 37 mm M6 gun. Armor protection ranged from 25 mm to 101 mm. Secondary armament consisted of two .50 caliber machine guns in a bow mount, two .30 caliber machine guns in the front plate, and additional machine guns on the turret roof for anti-aircraft and commander use. The vehicle was powered by a Wright G-200 9-cylinder air-cooled radial gasoline engine. Transmission options included a Timken mechanical model, a torque converter, or an electric transmission. The crew consisted of six personnel: commander, gunner, loader, driver, assistant driver, and an ammunition passer. Evaluation at Fort Knox and Aberdeen Proving Ground identified design deficiencies, including an awkward internal layout, a high silhouette, and reliability concerns.

Production began in December 1942, but the US Armored Corps ultimately favored the M4 Sherman due to its superior reliability, lower cost, and easier transportability. Consequently, the M6 production target was reduced from several thousand to 40 units. The M6 never saw combat and was restricted to service within the United States. Several units were used for propaganda purposes and performance displays during war bond drives. In 1944, a variant designated M6A2E1 was developed with a 105 mm gun and increased armor protection for specialized assault roles, but the proposal was rejected for operational use. The M6 was declared obsolete in December 1944. The British Army utilized the M6 horizontal volute spring suspension system for the Excelsior prototype tank, and one T1E1 prototype remains preserved at the United States Army Ordnance Museum.