M103 120mm gun combat tank (T43)

The 120mm gun combat tank M103 was the only one of a series of late war and early post-war American heavy designs to actually reach production, and was a lighter version of the earlier Heavy Tank T34.

In the immediate aftermath of the Second World War the Stillwell Board recommended the development of light, medium and heavy tanks, but post-war budget cuts meant that work was slow. A series of late-war projects were under way, starting with the closely related Heavy Tank T29 and Heavy Tank T30 and the less complex Heavy Tank T32, while in May 1945 work began on the Heavy Tank T34, which was to carry a modified 120mm anti-aircraft gun on a chassis developed from the T29 and T30. The T34 had a combat loaded weight of 143,600lb, and neither the US Army nor the Marine Corps was interested in such heavy tanks.

By 1948 the brief period of post-war optimism over relations with the Soviet Union was over. The year began with the Communist seizure of power in Czechoslovakia, and later saw the Berlin Airlift. The increasingly threatening international scene encouraged the resumption of work on new heavy tanks.

The Detroit Arsenal examined the T34 to see if was possible to produce a lighter vehicle. They concluded that it should be possible to produce a lighter vehicle by shortening the hull, using a new lighter 120mm gun and using heavily sloped armour. On 1 December 1948 the new idea was laid out in OCM 32530, as the Heavy Tank T43.

The new tank was to use the 80in turret ring of the T34. It would have seven road wheels, one less than the T34, but wider tracks and its lighter weight meant that ground pressure remained similar. It would carry a crew of four - driver, gunner, loader and commander, compared to the six of the T34. It would be armed with a lighter 120mm gun and have up to 5in of armour. It would be powered by the 810hp Continental AV-1790 engine - more powerful versions were available but would require the development of a new transmission.

During 1949 the Detroit Arsenal continued to work on the design, and by October they had come up with a very different hull and turret shape. This time the T43 was to have a elliptically shaped cast hull and turret, which was believed to give the same levels of protection at lower weight. This was examined in October and December 1949, and the new specifications were then laid out in OCM 33333 on 24 April 1950. This covered the new hull and turret shape, a larger 85in turret ring, and the replacement of the automatic loading equipment with a second loaders. At this point the tank was still designated as the Heavy Tank T43, but in November 1950 it became the 120mm gun tank T43.

Work on the T43 became more urgent after the outbreak of the Korean War in June 1950. The most modern tanks in the US arsenal were a number of M46 Pershings, which were rebuilt versions of the M26 Pershing. New tanks were urgently needed, and in December 1950 Chrysler received an order for 80 T43s. This was later increased to 300 tanks. An order for six pilots had already been placed. The new tank was to be used by the US Army and the Marine Corps. The Army got 80, the Marines 220.

The first T43 pilot was delivered to the Aberdeen Proving Ground in June 1951. The fourth, fifth and sixth pilots incorporated changes introduced after the first trials, and on 17 July 1952 production tanks that included these changes became the 120mm gun tank T43E1. They used a new 120mm gun with a higher muzzle velocity, and a more conventional recoil system.

A total of 300 T43E1s was built by Chrysler in 1953-54. Trials began in May 1953, using the sixth pilot and the eighth production vehicle. The rushed development process now began to cause problems. The T43E1 was rejected as unsatisfactory for army use because of problems with the turret and guns controls and the sighting systems, all of which were underperforming and unreliable. The 120mm ammo was also unacceptably inaccurate. In August 1955 the T43E1 tanks were placed into storage while work began on fixing the problems.

In November 1955 a total of 98 modifications were recommended. These changes were approved in February 1956 and the T43E1 was standardised as the 120mm gun combat tank M103 on 26 April 1956.

At the same time work began on a more ambitious program, to solve the turret and gun control programmes. Two pilots were approved on 22 April 1954, as the 120mm gun tank T43E2. Most of the changes in the new design came in the turret. The gunner was moved to the front right. A new electric amplidyne turret control system was installed. The coaxial machine gun to the right of the 120mm was replaced with a telescope to help the gunner. A new T52 stereoscopic range finder and T33 ballistic computer were installed.

The M103 was dominated by its massive cast turret. This had curved sides, and a raised rear section. The cast hull had a pointed front, with the upper and lower sections both curving gently. It used the AV-1790-5B engine and CB-850-4B transmission, with a heat deflector panel under the turret bustle to prevent overheating when it was sitting over the engine.

Six of the Army's M103s had been used for experiments, but 74 were brought up to the M103 standard. In 1958 they went to the 899th Tank Battalion in Europe, which then became the 2nd Heavy Tank Battalion, 33rd Armor, in May 1958. In service the M103 performed well. Despite its extra weight it could reach most of the same places as the M48, and the 120mm gun was much more powerful than their 90mm guns. Even so the Army had little interest in the M103, having returned to the dislike of heavy tanks that had blighted their Second World War armoured forces.

In contrast the Marine Corps welcomed the M103, seeing it as a valuable infantry support weapon. The Marines operated 220 M103s, and in 1959 upgraded 219 of them to the M103A1 version, implementing the changes introduced on the T43E2. 153 were later upgraded to the M103A2 version, with more modern propulsion (the same 750hp diesel engine used in the M60) and fire control systems. Although they remained in use for well over a decade, the Marine Corps M103s never saw combat. 

In both cases the M103 was replaced by the M60. The Army had made the switch by 1963. The Marine M103s were declared obsolete in 1972, and over the next year or so replaced by the M60. The M60 was twelve tons lighter, and was the first US Main Battle Tank, combining the firepower and armour of the heavy tank with the mobility of lighter vehicles.

Stats
Length with Gun: 448.6in
Hull Length:  275.3in
Hull Width: 143in
Height: 140.1in
Crew: 5
Weight: 125,000lb combat loaded
Engine: 810hp Continental AV-1790 V-12 air cooled engine
Max Speed: 21mph
Max Range: 80 miles road range
Armament: One 120mm Gun M58 and coaxial .30in MG in turret, one remote controlled .50in MG on commander's cupola

Armour

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