T57 was a heavy tank developed in the U.S. in the mid-50's, Is a slightly modified version of the US T43E1 prototype that further evolved into M103 tank.
Development history
T58 prototype version fitted with a 155 mm gun in oscillating turret
In October 12, 1951, a decision was made to develop a prototype of a heavy tank with an oscillating turret, a new idea at the time invented by the French AMX company, and adopted on a highly successful AMX 13 light tank, and no so successful AMX 50 series of heavy tanks. New American tank, designated T57 (according to the American post-war terminology - "120-mm gun tank T57“), was based on the chassis of the T43 tank (prototype that further evolved into M103) with a brand new oscillating turret that hosted a powerful 120 mm T123E1 gun.
Oscillating turret
The oscillating turret design, lacking a conventional gun-mantlet, is in two separate parts, with an upper and lower part connected by two hinge bolts or pivots, the gun being fixed within the upper section. The horizontal movement of the gun, traversing, is conventional, but the vertical movement, elevation, is achieved through the pivoting of the entire upper section with respect to the lower section. This method of elevation has two main advantages. Firstly it allows for a smaller turret volume, as no internal space is needed for the vertical movement of the gun breech. Secondly, it allows the use of a relatively simple auto-loader fed by multiround magazines, achieving a very high rate of fire for as long as the magazines were loaded. Automatic loader was located in the back of a massive tower, and consisted of the feeder drum with 8 rounds. The drum was loaded by a hydraulic actuator, and the commander or gunner could pick three different types of ammunition. Spent cartridges were ejected through a special hatch on the roof of the turret.
Design flaws
Main armament of the tank was 120 mm T123E1 gun with the rifled barrel, and placing such a big, powerful and heavy weapon into the oscillating turret was plagued by various problems. Handling the immense recoil of the gun, and stabilizing the heavy turrets were among the issues that were never compleatly solved. Tank had the crew of 4, where loaders job was to reload the drum after all round have been fired. The tank carried a total of 10 additional rounds in the ammo rack, making a total ammo load to 18 rounds. Another issues were limited gun elevation (due to the back of the turret movement being limited by the hull), problems with ammo protection at certain angles (oscillating turret doesn't have mantlet that solves this problems on classic turrets) and the lack of protection against radiation and weapons of mass destruction, which was considered very important back in the fifties and sixties.
Fate
The development was very slow and interest in the tank started to fade. Changing priorities in favor of the development of small, aero transportable tanks led to the cancellation of the project in January 1957, before the prototype reached operational status and could be tested. No photos of the assembled prototype T57 with 1200 gun has survived.
