M103

Design and Development

Like the contemporary British Conqueror tank, the M103 was designed to counter Soviet heavies such as the Josef Stalin tank or the T-10 if a conventional World War III broke out. Its long-ranged 120 mm cannon was designed to hit enemy tanks at extreme distances, but it was never used in combat. In 1953-1954 a series of 300 tanks, initially designated T43E1, were built by Chrysler at the Newark plant. Testing was unsatisfactory, and the tanks were all stored in August 1955. Only after recommending improvements, on 26 April 1956 the tank was standardized as the M103 Heavy Tank. Of the 300 T43E1s built, 80 went to the US Army (74 of which were rebuilt to M103 standard), and 220 were accepted by the US Marine Corps, to be used as infantry support, rebuilt to improved M103A1, then M103A2 standards. The successive versions of the M103 shared many components with the M47 and M48 Patton tanks and the M60, which, with the exception of the M60 (a main battle tank) were all considered 90 mm gun (medium) tanks. Tracks, rollers and suspension elements were the same, with some modification to take into account the greater weight. The engine and transmission were never modified enough to give the extra power needed for the greater weight of the M103, and as a result, the tank was relatively underpowered and the drive systems were fragile. The turret of the M103 was larger than that of the M48 or the M60 to make room for the huge 120 mm gun and the two loaders assigned to it, in addition to the gunner and the commander. The driver sat in the hull. The gun was capable of elevation from +15 to -8 degrees. The armor is made from welded rolled and cast homogeneous steel of varying thickness.

• Hull front: 100–130 mm (4.0–5.3 in)
• Hull side: 76 mm (3.1 in)
• Hull top: 25 mm (1 in)
• Turret mantlet: 250 mm (10.2 in)
• Turret front: 180 mm (7.3 in)
• Turret side: 76 mm (3.1 in)
• Turret top: 38 mm (1.5 in)

Service

In Europe, the US Army fielded only one battalion of heavy tanks, from January 1958, originally assigned to the 899th Armor, later redesignated the 2/33rd Armor. The US Army heavy armor battalion, in contrast to other armor units, was organized into four tank companies, composed of six platoons each, of which each platoon contained three M103's, for a total of 18 tanks per company. Standard US Army armor battalions at the time had three companies per battalion, each with three five-tank platoons, with 17 tanks per company (two tanks were in headquarters platoon). The US Marine Corps assigned one M103 company to each of its 3 Marine tank battalions, including its Marine reserve units. While the US Army deactivated its heavy armor units with the reception of the new M60 series main battle tanks in 1963, the remaining M103s stayed within the US Marine Corps inventory until they began receiving the M60 series MBT. With the disappearance of the heavy tank from US forces came the full acceptance of the main battle tank in 1960 for the US Army, and 1973 for the US Marine Corps. Although the 21st century's M1 Abrams MBT utilizes the same caliber of main gun, the 120 mm, the M103's cannon was a rifled gun firing a fixed round, ejecting a lengthy brass shell casing (34.69 inches in length for the armor-piercing rounds). The M1 tank's 120 mm main gun is a smooth bore (no rifling) firing a semi-caseless round, ejecting only a back cap of the original loaded round; the bulk of the 120 mm shell's casing is consumed during firing. Ammunition fired by the M103's M58 cannon included:

• APBC-T M358 Shot
• HEAT-T M469 Shell
• HE-T M356 Shell
• TP-T M359E2 Shot

Variants

• T43E1 1953. 300 built.
• M103 1957. 74 converted.
• M103A1 1959. 219 converted or rebuilt. New sight (Stereoscopic T52) and T33 ballistic computer. Removed one coaxial machine gun. New turret electric amplidyne system traverse. Turret basket.
• M103A2 1964. 153 converted or rebuilt. New 750 hp (559 kW) diesel engine from the M60 tank, increasing the road range to 480 km and maximum speed to 37 km/h. New sight coincidence XM2A.