The .50 Browning Machine Gun (.50 BMG) or 12.7×99mm NATO 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 greatly scaled-up .30-06 cartridge.[citation needed] Under STANAG 4383, it is a standard cartridge for NATO forces as well as many non-NATO countries.[1] The cartridge itself has been made in many variants: multiple generations of regular ball, tracer, armor-piercing, incendiary, and saboted sub-caliber rounds. The rounds intended for machine guns are linked using metallic links.The .50 BMG cartridge is also used in long-range target and sniper rifles, as well as other .50-caliber machine guns. The use in single-shot and semi-automatic rifles has resulted in many specialized match-grade rounds not used in .50-caliber machine guns. A McMillan Tac-50 .50 BMG sniper rifle was used by Canadian Army Corporal Rob Furlong of the PPCLI to achieve what was then the longest-range confirmed sniper kill in history, when he shot a Taliban combatant at 2,430 meters (2,657 yards) during the 2002 campaign in the Afghanistan War.[2] (This was surpassed in 2009 by a British sniper in Afghanistan with 2,475 meters (2,707 yards) using a .338 Lapua Magnum (8.58×70 mm) rifle.)[3][4]A former record for a confirmed long-distance kill was set by U.S. Marine sniper Carlos Hathcock in 1967, at a distance of 2,090 metres (2,286 yd);[5] Hathcock used the .50 BMG in an M2 Browning Machine Gun equipped with a telescopic sight. This weapon was used by other snipers, and eventually purpose-built sniper rifles were developed specifically for this round.DARPA (Defense Advanced Research Projects Agency) has contracted with Lockheed Martin to develop the EXACTO program, including .50-caliber bullets complete with microprocessors and steering vanes that allow the bullet to adjust its trajectory mid-flight when the flight path has changed.[6][7][8]A wide variety of ammunition is available, and the availab