M73 machine gun
The M73 and M219 are 7.62 mm NATO caliber machine guns designed for tank use. NATO no longer uses them, but they were used on the M48 Patton and M60 Patton MBT series (including the M728 Combat Engineer Vehicle), as well as the MBT-70 prototype vehicles, and on the M551 Sheridan Armored Reconnaissance / Airborne Assault Vehicle (AR/AAV). Design and development. Designed primarily as a coaxial machine gun by the Rock Island Arsenal and produced by General Electric, the M73 was developed as a replacement for the M1919A4E1, M1919A5, and M37 machine guns that continued to serve  in the immediate post–World War II environment. The "Machine Gun, 7.62-MM, M73" was officially adopted in 1959. It is an air-cooled, recoil-operated machine gun, but also using cartridge gases to boost recoil. Though designed as a simplified alternative to the M1919 series, it is of almost identical weight. The weapon is fitted with a quick-change barrel, pull-chain charging assembly, and can be made to feed from the left or the right hand side (though the left-hand feed is more common). An attempt to make the M73 useful as a flexible infantry gun saw  the weapon fitted with sights and a pistol grip trigger as the "Machine Gun, 7.62-MM, M73C". Equally unpopular, very few of these weapons were produced. Sources claim that it saw limited use in Vietnam. The M73 suffered from numerous malfunctions and was prone to jamming. An improved M73E1 was eventually developed in 1970 with a simplified ejection system, being type classified as the "Machine Gun, 7.62-MM, M73A1". In 1972, it was decided that this weapon was sufficiently different from its predecessor and was redesignated "Machine Gun, 7.62-MM, M219". These weapons were eventually replaced by the M60E2 and  M240 machine gun, and vehicles still in service using the M73 series were refitted with these weapons.