M103

Overview
The M103, or 120 mm Gun Combat Tank M103, was a heavy tank of the United States Army and Marine Corps during the post-war and Cold-War periods. The M103 was the last U.S. heavy tank, and was designed to fulfill a similar role to the British Conqueror. Both, however, were eventually replaced by the Main Battle Tank. The M103 was completely taken out of service by 1974.

Design
Like the Conqueror, the M103 was designed to destroy the JS-3, a Soviet Heavy Tank which was causing considerable fear within NATO. However the IS-3 was not as potent as the Western Powers had suspected, and thus the M103 and Conqueror were rather overkill. In 1953 to 1954, the first M103s entered production with Chrysler. The vehicle was originally designated T43E1. It began trials with the US Army, and proved to have severe deficiencies in its gun control equipment and turret layout. In 1955 they were put into storage, and an improvement plan was issued. After 98 vehicles received these modifications, the tank was designated M103. About 80 of the new M103s went to the Army, and the remaining T43E1s were taken by the Marine Corps for infantry support. The Marines eventually upgraded these to M103A1 and A2 standard.

The M103 was equipped with a two-piece elliptical hull similar to that of an M48. The suspension consisted of seven double road wheels per side, attached to long-arm torsion bar suspension. The track was 28 inches wide, and featured a metal-backed rubber chevron arrangement. A Continental AV-1790 810 hp engine was placed at the rear of the tank, which allowed the 60-ton vehicle to reach a maximum speed of around 22 mph. The transmission was a General Motors CD-810-4 3 speed transmission unit. The drive-train was shown to be insufficient during trials, and the powerpack was underpowered. While the engine was successful on the M48/60 tanks, the M103 was much heavier. Furthermore, the vehicle was fuel-thirsty, and its range was limited. The USMC M103A2 introduced a new powerpack, an AV-1790-2 diesel, which helped, however the vehicle remained difficult to employ due to its weight. The massive turret and the other large armor pieces were cast, to ease production. The armor was also amazingly sloped, which gave it better protection than the previous T-29. Despite this, the M103 was lighter. The Glacis was pike-like, similar to that of the JS-3, and the single-piece turret provided around 250 mm of protection.

The 120 mm rifled L1 gun fired two-piece ammunition. This required a crew of six, to accommodate the two loaders.

M103
The M103 originally placed the gunner at the rear of the turret, so he could operate the stereoscopic rangefinder. The loaders were placed at the front of the turret, and two co-axially mounted machine guns were added to make use of space. This layout caused problems, however, and the gunner was moved back to the turret front in the A2 version of the vehicle. This turret layout worked much better.

Action
The M103s in Army service were in the 899th Tank Battalion (Eventually re-designated 2nd Battalion 33rd Armor). The M103s served in Europe, primarily in West Germany, and functioned along the same lines as the British Conqueror. They were meant to use their powerful 120 mm guns to destroy Soviet vehicles at long ranges, and to support the lighter M60 and M48 tanks.

The Marine Corps arranged their M103s into one company per tank battalion. Some M103s were in reserve. The vehicle never saw combat. As the M60 main battle tank began to take over U.S. armored divisions, the M103 began to disappear. All army M103s were retired in the 1960s, and the USMC phased theirs out in the 1970s. The M103 was ultimately the last American heavy tank, as the main battle tank quickly made the type obsolete.