M6 heavy tank

Heavy Tank M6
T1E1 prototype
Type	Heavy tank
Place of origin	United States
Service history
In service	trials only
Used by	United States Army
Wars	World War II
Production history
Designer	US Army Ordnance Corps
Manufacturer	Baldwin Locomotive
Number built	40
Variants	6
Specifications (M6)
Weight	126,500 lb (57.4 tonnes) combat loaded
Length	27 ft 8 in (8.43 m) gun forward
Width	10 ft 3 in (3.12 m) over track armor
Height	9 ft 10 in (3.0 m) to turret roof
Crew	6 (commander, gunner, driver, assistant driver, loader, assistant loader)
Armor	25–83 mm
Main armament	1 × 3in (76.2 mm) gun M7 (75 rounds) 1 × 37 mm (1.46 in) gun M6 (202 rounds)
Secondary armament	2 × .50 cal (12.7mm) Browning M2HB machine guns, hull (6,900 rounds) 2 × .30 Browning M1919A4 machine guns, one fixed (bow), one flexible AA (5,500 rounds)
Engine	1,823 in3 (29.88 L) Wright G-200 9-cylinder gasoline 825 hp at 2,300 rpm
Power/weight	15.7 hp/tonne
Transmission	Timken mechanical model 16001, three speeds (two forward, one reverse); rear drive sprocket
Suspension	Horizontal volute spring
Ground clearance	20.5 in (52 cm)
Fuel capacity	477 US gallons (1,810 L)
Operational range	100 miles (160 km)
Speed	22 mph (35 km/h)

The Heavy Tank M6 was an American heavy tank designed during World War II. The tank was produced in small numbers and never saw combat.

Because of limited budgets for tank development in the interwar years, at the outbreak of World War II the US Army possessed few tanks, though it had been keeping track of the use of tanks in Europe and Asia. Successful employment of armored units in 1939–40, mostly by the Germans, gave momentum to a number of US tank programs, including a heavy tank program. The United States possessed a massive industrial infrastructure and large numbers of engineers that would allow for mass production of tanks.

Following the Chief of Infantry recommendation from 20 May 1940, the US Army Ordnance Corps started to work on a 50-ton heavy tank design. Initially a multi-turreted design was proposed, with two main turrets armed with low-velocity T6 75 mm (2.95 inch) guns, one secondary turret with a 37 mm gun, and a coaxial .30 caliber (7.62 mm) machine gun, and another secondary turret with a 20 mm gun and a coaxial .30 caliber machine gun. Four .30 caliber machine guns were to be installed in ball mounts, two in the glacis (front) plate and two in the rear corners of the hull. The project was approved on 11 June 1940 and the vehicle received the designation Heavy Tank T1. The design was somewhat similar in concept to multi-turreted breakthrough tanks developed in Europe in the 1920s and throughout the 1930s, such as the 1925 British Vickers A1E1 Independent or the Soviet T-35 of the early 1930s. Disadvantages of these "land dreadnoughts", namely their excessive size, difficulty in coordinating actions of the crew, and high production costs, led to abandonment of the concept in Europe.

By October, the US developers reached the same conclusion as their European counterparts. The armament was changed to a single vertically stabilized 3-inch (76.2 mm) gun and a coaxial 37 mm gun in a single three-man turret with both manual and electric traverse. The turret had a commander's cupola identical to that of the M3 Medium Tank. Additional armament consisted of two .50 caliber machine guns in a bow mount (operated by the assistant driver), two .30 caliber machine guns in the front plate (fired electrically by the driver), one .30 caliber in the commander's cupola and one .50 caliber in a rotor mount for anti-aircraft use in the right rear of the turret roof (operated by the loader). The crew consisted of commander (seated in the turret left), gunner to the right of the gun, gun loader (turret), driver and assistant driver in the front left and right of the hull respectively, and another crewman in the hull to pass ammunition to the turret.