The .50 Browning Machine Gun (12.7 × 99 mm NATO) or .50 BMG is a cartridge developed for the Browning .50 Caliber machine gun in the late 1910s. Entering service officially in 1921, the round is based on a scaled-up 30-'06 cartridge. The cartridge itself has been made in many variants: multiple generations of regular ball, tracer, armor piercing, incendiary, and saboted sub-caliber rounds.