The M73 and M219 are 7.62 mm NATO caliber machine guns designed for tank use.They were also used in a twin mount in the turret of the V-100 Commando (M706) light armored car during the Vietnam War.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.It is an air-cooled, recoil-operated machine gun, but also using cartridge gases to boost recoil.An improved M73E1 was eventually developed in 1970 with a simplified ejection system, being type classified as the Machine Gun, 7.62-MM, M73A1.