The .50 BMG (short for Browning Machine Gun) (12.7×99mm NATO in metric) is a large caliber machine gun cartridge. It is based on the .30-06 Springfield, in a largely upscaled form factor.
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 that are not used in .50 caliber machine guns.
A wide variety of ammunition is available, and the availability of match-grade ammunition has increased the usefulness of .50 caliber rifles by allowing more accurate fire than lower quality rounds.
DARPA (Defense Advanced Research Projects Agency) has developed the EXACTO program, .50 caliber bullets complete with microprocessors and steering vanes that allow the bullet to adjust its trajectory mid-flight to stay on target when the flight path has been altered by uncontrollable variables.
Records for longest-range sniper kills
In June 2017, a McMillan TAC-50 sniper rifle was used by Canada's Joint Task Force 2 to kill an ISIL insurgent in Iraq from a distance of 3,540 meters (3,870 yards), setting the current world record for the longest-range confirmed kill shot in military history.
Previously, Canadian Corporal Rob Furlong, also using the TAC-50, brought off the 3rd 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. This record was eclipsed by two confirmed kills in November 2009 in Afghanistan against Taliban machine gunners by Craig Harrison, a member of the British Household Cavalry, using an Accuracy International AWM L115A3 long-range rifle chambered in .338 Lapua Magnum. The shots were measured by GPS at 8,120 ft or 2,706 yards (2,474 m).
The previous record for a confirmed long-distance was set by U.S. Marine sniper Carlos Hathcock in 1967, the distance was 2,286 meters (2,500 yards, 7,500 feet) or 1.42 miles (2.29 km). 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 especially for this round.
Developed early in the 1910s and first tested with Browning's prototype .50 cal machine gun in 1918, it was introduced into service in 1921 for the M1921, the forerunner to the M2 Browning Machine Gun.
It is still the most common NATO heavy machine gun round just as its companion the M2 is the most common NATO heavy machine gun, and is now also used in anti-materiel rifles.
War crime urban legend
A persistent claim is that it is a war crime to fire .50 BMG rounds at infantry. This is not true, and is actually the result of instructions regarding a totally different .50 round, .50 BAT (12.7×77mm BAT) a spotting rifle round used for the M40 Recoilless Rifle.
Gun crews of these weapons were told not to fire their spotting rifle at infantry, due to a combination of desire not to give away the hard-to-move 462-pound weapon's location, and due to fears that the round itself (a point-detonating incendiary designed to produce a visible puff of smoke on impact) might be considered an explosive round weighing less than 400 grams and therefore a violation of the St. Petersburg Declaration of 1868. At some point it appears the context of the order "don't fire the .50 at infantry" was forgotten, resulting in a situation where this order is thought to refer to the M2.