Back into the 70s...

About the MBT-5H

The MBT-5H is a NATO tank hybrid of: Type 90, Leopard 2A4, M1A1 Abrams. It uses the Type 90 and Leopard 2A4 Turret Hybrid, and uses the M1 Abrams hull. It uses the M256 120mm Smoothbore Cannon.

About the M256 Smoothbore Cannon

The M256 is an American 120 mm smoothbore tank gun. It is a licensed-built German-designed Rh-120 L44 gun tube and combustible cartridges with an American-designed mount, cradle and recoil mechanism. It is primarily used by the M1 Abrams main battle tank.

A number of considerations had led the U.S. Army and its contractors to favor the Army's standard M68 105 mm gun over Germany's 120 mm Rheinmetall Rh-120 smoothbore gun for the XM1 Abrams. To begin with, the 105 mm gun was "the smallest, lightest, and least costly gun adequate for the job."[1] Indeed, new kinetic energy ammunition for the weapon then under development by the Army promised to extend the gun's usefulness well into the future. And because the Army's other tanks, the M60 and the upgraded M48, as well as the tanks of virtually every other NATO nation, used the 105 mm gun, mounting that gun on the XM1 promised to increase standardization within the alliance. Moreover, the continuing development of the new ammunition for the XM1 would in effect automatically upgrade every other gun in NATO. For all of these reasons, the XM1's development proceeded "on the assumption that the 105 mm gun would probably be the eventual main armament."[1][2] The tripartite British–American–German gun trials of 1975 produced a general agreement in the U.S. Defense Department that at some future point, a 120 mm gun of some design would be added to the XM1. Anticipating this, Chrysler and GM had both made changes to their tanks during development to make them compatible with a variety of main guns.[3] After head-to-head testing between the Royal Ordnance L11A5 and the Rheinmetall Rh-120,[citation needed] the Secretary of the Army announced in January 1978, that the Rheinmetall 120 mm gun would be mounted on future production versions of the XM1.[4] Although the L11/M256 120mm gun was chosen to be the main weapon of the Abrams in 1979, the improved ammunition for the gun still was not fully developed, thus delaying its fielding until 1984.[5] A license was obtained for its manufacture at Watervliet Arsenal at Watervliet, New York.[6] From October 1980 to September 1981, Watervliet Arsenal fabricated eight XM256 cannons and fourteen spare tubes.[7]

About the M830 shell

The M830 is an American high explosive anti-tank (HEAT) high explosive multi purpose cartridge which has anti-armor and anti-personnel capabilities.[1] This round is meant for the 120 mm M256 main gun of the M1A1 and M1A2 Abrams. The M830 HEAT-MP-T, 120-mm cartridge is a direct translation of the German DM12A1 round with the exception that a United States design fuze system and explosive (Composition A3, Type 11) is used. The propellant system utilizes a metal cartridge case base with a rubber obturator at the stub case mouth, M123A1 Primer, and a combustible wall which encapsulates stick propellant within six containment devices to prevent spillage should breakage or separation occur. The cartridge is black with yellow markings, weighs approximately 53.4 lb (24.2 kg), and has a length of 38.6 inches (981 mm).[2] The round was praised for its performance during the 1991 Gulf War.[3] It is no longer manufactured and has been replaced by the M830A1.[4]

The M830A1, the M830's successor, provides greater lethality through a higher initial velocity and a multi-purpose fuse. The M830A1 is a fin-stabilized round with a discarding sabot and tactical service round with tracer. The baseline design contains a propulsion system consisting of a metal case base, a combustible cartridge case, case adapter, nineteen perforated hexagonal JA2 propellant, a propellant containment device (cloth bag), and an M129 primer (all are currently used on the M829A1). The conical nose of the projectile consists of the FISA coupled to the warhead body and the M74 Proximity Switch coupled to the FISA. The FISA is a secondary switch which closes upon impact against ground target. The M74 Proximity Switch (primary switch) contains two parallel "switches", either of which, when closed, will complete the M774 firing circuit. One switch closes upon direct impact with a target. The other is an electronic switch (a transistor) which "closes" when the proximity switch senses the presence of an air target. For all modes, a flexible electrical cable provides a path between the switches and M774 base element. In any of the functioning modes of the M830A1 fuzing system, the J1 connector of the M774 fuze is returned to "ground potential" which completes the fuze firing circuit.[2] The cartridge is black with yellow markings, weighs 49.2 lb (22.3 kg), with the projectile accounting for 25.1 lb (11.4 kg), and has a length of 38.74 inches (98.4 cm).[5] It is capable of engaging helicopters thanks to its dual-purpose fuze that offers impact or proximity modes.[6] The M830A1 was first fielded in 1994.[7]

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