The M53 Self-Propelled Assault Gun was developed via automotive components taken from existing M46 and M47 Patton medium tanks appearing during the Cold War. The M53, with its 155mm main gun, provided long-range fire support to allied positions and its self-propelled tracked nature ensured that it could keep pace with mechanized formations and provide cross-country capabilities. The series was adopted in 1952 and went on to see service with both the United States Army and Marine Corps. Production of the type was handled through Pacific Car & Foundry Company.
Unlike the M46/M47 combat tank series, the M53 saw her internals rearranged to make space for the addition of a turret superstructure. This meant that the engine and transmission system were now fitted to the front of the vehicle as opposed to the rear. Additionally, the driver was relocated from his front-left hull position to the front-left of the boxy turret superstructure. The entire crew complement was six personnel including the driver, commander, gunner and ammunition handlers. The main gun was a 155mm M46 series fitted onto an M86 mounting and afforded 20 projectiles. A .50cal Browning M2HB heavy machine gun served as a self-defense measure and given 900 rounds of ammunition (the gun fitted to the turret roof at the commander's cupola). Armor protection included a rolled homogenous steel hull with welded assembly which secured against small arms fire and artillery spray. The hull utilized many flat, vertical and horizontal faces with a very shallow glacis plate over the powerpack. The turret consisted of several vertical panels and a flat roof with a squared-off rear. The 155mm gun barrel was of a particularly lengthy design and lacked any sort of recoil-reducing muzzle compensator. A large toothed spade was fitted to the rear of the turret structure for stabilization when firing. Access to the turret was through a rectangular door fitted along the right side and roof hatches were present as well. One of the key limitations of the M53 design was its turret which allowed for only 30-degrees traversal to the right or left through a manual-/hydraulic-powered system. Elevation ranged from +65 to -5 degrees.
The vehicle was powered through a Continental AV-1790-5B 12-cylinder gasoline-fueled engine outputting at 810 horsepower and mated to a General Electric CD-850-4 transmission with 2 forward gears and 1 reverse. Steering was initially through a "wobble stick" arrangement. Top road speed was 35 miles per hour with an operational range of 150 miles. As the M46 and M47 designs were improved, the M53 absorbed some of their improvements in turn. This included use of the Continental AV-1790-7B series engines and CD-850-4B series transmission systems. A steering wheel eventually replaced the wobble stick steering arrangement.
The base running gear of the M53 incorporated seven double-tired road wheels to a track side with the drive sprocket at the front. There was no dedicated track idler at the rear of the vehicle which gave the track linkage system a "drooped" appearance at the rear. Three track return rollers guided the upper track regions.
With the arrival of the newer M55 (mounting a 203mm main gun), the United States Army upgraded its M53 fleet to the standard (beginning in 1956). However, the USMC decided to retain their smaller-caliber M53 systems for the interim.