Gun calibre

Increases in gun calibre are well illustrated by the British Centurion, which started in 1945 with a 76-mm gun but in 1948 was rearmed with an 83.8-mm gun and in 1959 with an even more powerful 105-mm gun. Moreover, during the 1950s the capabilities of British tank units were augmented by a small number of Conqueror heavy tanks armed with 120-mm guns, and in the early 1970s the Centurions were entirely replaced by Chieftains armed with new and more-effective 120-mm guns.

Similar increases took place in the calibre of Soviet tank guns. After World War II the basic T-34/85 tanks armed with 85-mm guns were replaced by T-54 and T-55 tanks armed with 100-mm guns. They were followed in the 1960s by the T-62, with a 115-mm gun, and in the 1970s and ’80s by the T-64, T-72, and T-80, all with 125-mm smoothbore guns. The JS-3 and T-10 heavy tanks with their less powerful 122-mm guns had by then been withdrawn. This left the Soviet army in the same position as others of having a single type of battle tank as well-armed as contemporary technology would allow.

For a time the U.S. Army also subscribed to a policy of developing heavy as well as medium tanks. But the heavy M103 tank, armed with a 120-mm gun, was only built in small numbers in the early 1950s. As a result, virtually the only battle tanks the U.S. Army had were the M46, M47, and M48 medium tanks, all armed with 90-mm guns. After the mid-1950s the M47 tanks were passed on to the French, Italian, Belgian, West German, Greek, Spanish, and Turkish armies, and during the 1960s the M48 began to be replaced by the M60, which was armed with a U.S.-made version of the 105-mm gun developed for the British Centurion.

The same 105-mm gun was adopted for the Pz. 61 and Pz. 68 tanks produced in Switzerland, the West German Leopard 1, the Swedish S-tank, the Japanese Type 74, and the Mark 1 and 2 versions of the Israeli Merkava. It was also retained in the original version of the U.S. M1 Abrams tank developed in the 1970s, but the subsequent M1A1 version of the 1980s was rearmed with a 120-mm gun originally developed in West Germany for the Leopard 2 tank. The British Challenger, introduced in the 1980s, was also armed with 120-mm guns, but these were still of the rifle type.

Ammunition

The last years of World War II saw the development of more- effective antitank ammunition with armour-piercing, discarding-sabot (APDS) projectiles. These had a smaller-calibre, hard tungsten carbide core inside a light casing. The casing fell away on leaving the gun barrel, while the core flew on at an extremely high velocity. The APDS, which was adopted for the 83.8-mm gun of the Centurions, was fired with a velocity of 1,430 metres (4,692 feet) per second. By comparison, earlier full-calibre, armour-piercing projectiles had a maximum muzzle velocity of about 900 metres (3,000 feet) per second. With this shell the Centurion’s 83.8-mm gun could penetrate armour twice as thick as could the 88-mm gun of the German Tiger II of World War II.

An alternative type of armour-piercing ammunition developed during the 1950s was the high-explosive antitank (HEAT) shell. This shell used a shaped charge with a conical cavity that concentrated its explosive energy into a very high-velocity jet capable of piercing thick armour. The HEAT round was favoured by the U.S. Army for its 90-mm tank guns and also by the French army for the 105-mm gun of its AMX-30 tank, introduced in the mid-1960s. However, during the 1970s both APDS and HEAT began to be superseded by armour-piercing, fin-stabilized, discarding-sabot (APFSDS) ammunition. These projectiles had long-rod penetrator cores of tungsten alloy or depleted uranium; they could be fired with muzzle velocities of 1,650 metres (5,400 feet) per second or more, making them capable of perforating much thicker armour than all earlier types of ammunition.

During the 1960s, attempts were made to arm tanks with guided-missile launchers. These were to provide tanks with a combination of the armour-piercing capabilities of large shaped-charge warheads with the high accuracy at long range of guided missiles. The U.S. M60A2 and the U.S.-West German MBT-70 were armed with 152-mm gun/launchers firing standard ammunition as well as launching Shillelagh guided antitank missiles, and the AMX-30 was armed experimentally with the 142-mm ACRA gun/launcher. But the high cost, unreliability, and slow rate of fire of the missiles, together with the appearance of APFSDS ammunition and greatly improved fire-control systems, led to abandonment of gun/launchers in the early 1970s.

Fire control

The first major postwar advance in fire-control systems was the adoption of optical range finders, first on the M47 tank and then on the Leopard 1, the AMX-30, and other tanks. In the 1960s, optical range finders began to be replaced by laser range finders. In combination with electronic ballistic computers, these greatly increased the hit probability of tank guns. They became standard in all new tanks built from the early 1970s and were retrofitted in many of the earlier tanks.

Another major development was that of night sights, which enabled tanks to fight in the dark as well as in daylight. Originally of the active infrared type, they were first adopted on a large scale on Soviet tanks. Other tanks were fitted from the 1960s with image-intensifier sights and from the 1970s with thermal imaging sights. These latter were called passive because, unlike active infrared systems, they did not emit energy and were not detectable.

After World War II an increasing number of tanks were fitted with stabilized gun controls to enable them to fire more accurately on the move (i.e., to keep their gun barrels at a constant angle of elevation even while the tank was riding over bumps or depressions). At first some tanks, such as the T-54, had their guns stabilized only in elevation, but the Centurion already had stabilization in traverse as well as elevation, and this became standard beginning in the 1970s. Afterward tanks were also provided with independently stabilized gunners’, as well as commanders’, sights, the better to engage targets on the move.