Rheinmetall 120 mm gun

Rheinmetall 120 mm tank gun
A diagram of M256 gun
Type	Smoothbore tank gun
Place of origin	Germany
Service history
In service	1979–present
Used by	see the operators section
Production history
Manufacturer	Rheinmetall
Specifications
Weight	1,190 kg (2,620 lb) Gun barrel 3,317 kg (7,313 lb) Gun mount
Length	L/44: 5.28 m (17.3 ft) L/55: 6.6 m (22 ft)
Barrel length	44–55 calibers
Caliber	120 mm
Muzzle velocity	1,580 to 1,750 m/s (5,200 to 5,700 ft/s)
Effective firing range	4,000 meters (4,400 yd) with DM63 8,000 meters (8,700 yd) with LAHAT

The Rheinmetall 120 mm gun is a smoothbore tank gun designed and produced by the West German Rheinmetall-DeTec AG company, developed in response to Soviet advances in armor technology and development of new armored threats. Production began in 1974, with the first version of the gun, known as the L/44 as it was 44 calibers long, used on the German Leopard 2 tank and soon produced under license for the American M1A1 Abrams and other tanks. The American version, the M256, uses a coil spring recoil system instead of a hydraulic system. The 120-millimeter (4.7 in) gun has a length of 5.28 meters (17.3 ft), and the gun system weighs approximately 3,317 kilograms (7,313 lb).

By 1990, the L/44 was not considered powerful enough to deal with the future Soviet armour, which stimulated an effort by Rheinmetall to develop a better main armament. This first revolved around a 140-millimeter (5.5 in) tank gun named Neue Panzerkanone 140 ("new tank gun 140"), but later turned into a compromise which led to the development of an advanced 120 mm gun, the L/55, based on the same internal geometry as the L/44 and installed in the same breech and mount. The L/55 is 1.3 meters (4.3 ft) longer, giving an increased muzzle velocity to ammunition fired through it. As the L/55 retains the same barrel geometry, it can fire the same ammunition as the L/44.

This gun was retrofitted into German and Dutch Leopard 2s, and chosen as the main gun of the Spanish Leopard 2E and the Greek Leopard 2HEL. It was tested on the British Challenger 2 as a potential replacement for its current weapon, the rifled L30 120 mm cannon.

A variety of ammunition has been developed for use by tanks with guns based on Rheinmetall's original L/44 design. This includes a series of kinetic energy penetrators, such as the American M829 series, and high explosive anti-tank warhead warheads. Recent ammunition includes a wide range of new anti-personnel rounds and demolition munitions, giving tanks armed with the L/44 and its derivatives greater versatility on the modern battlefield. The LAHAT, developed in Israel, is a gun-launched missile which has received interest from Germany and other Leopard 2 users, and is designed to defeat both land armour and combat helicopters. The Israelis also introduced a new anti-personnel munition which limits collateral damage by controlling the fragmentation of the projectile.