John Browning had the idea for this round during World War I in response to a need for an anti-aircraft weapon, based on a scaled-up .30-06 Springfield design, used in a machine gun based on a scaled-up M1919/M1917 design that Browning had initially developed around 1900 (but which was not adopted by the U.S. military until 1917, hence the model designation). Armor-piercing incendiary tracer (APIT) rounds were especially effective against aircraft, and the AP rounds and API rounds were excellent for destroying concrete bunkers, structures, and lighter AFVs. The API and APIT rounds left a flash, report, and smoke on contact, useful in detecting strikes on enemy targets.
The development of the .50 BMG round is sometimes confused with the German 13.2 mm TuF, which was developed by Germany for an anti-tank rifle to combat British tanks during WWI; however, the development of the U.S. .50 caliber round was started before this later German project was completed or even known to the Allied countries. When word of the German anti-tank round spread, there was some debate as to whether it should be copied and used as a base for the new machine gun cartridge; after some analysis the German ammunition was ruled out, both because performance was inferior to the scaled-up .30-06 Springfield round and because it was a semi-rimmed cartridge, making it sub-optimal for an automatic weapon. The round's dimensions and ballistic traits are totally different. Instead, the M2HB Browning with its .50 caliber armor-piercing cartridges went on to function as an anti-aircraft and anti-vehicular machine gun, with a capability of completely perforating 0.875" (22.2 mm) of face-hardened armor steel plate at 100 yards (91 m), and 0.75" (19 mm) at 547 yards (500 m).
Decades later, the .50 BMG was chambered in high-powered rifles as well. The concept of a .50 caliber machine gun was not an invention of this era; this caliber (.50) had been used in Maxim machine guns and in a number of manual rapid-fire guns such as the original Gatling, although these were much lower power cartridges.
During World War II the .50 BMG was primarily used in the M2 Browning machine gun, in both its "light barrel" aircraft mount version and the "heavy barrel" (HB) version on ground vehicles, for anti-aircraft purposes. An upgraded variant of the M2 Browning "HB" machine gun used during World War II is still in use today. Since the mid-1950s, some armored personnel carriers and utility vehicles have been made to withstand 12.7 mm machine gun fire, thus making it a much less flexible weapon. It still has more penetrating power than lighter weapons such as general-purpose machine guns, though it is significantly heavier and more cumbersome to transport. Its range and accuracy, however, are superior to light machine guns when fixed on tripods, and it has not been replaced as the standard caliber for western vehicle mounted machine guns (Soviet and CIS armoured vehicles mount the 12.7×108mm NSV, which is ballistically similar to the .50 BMG.)
The Barrett M82 .50 caliber rifle and later variants were developed during the 1980s and have upgraded the anti-materiel power of the military sniper. A skilled sniper can effectively neutralize an infantry unit by eliminating several targets (soldiers or equipment) without revealing his precise location. The long range (1 mile+) between firing position and target allows time for the sniper to avoid enemy retribution by either changing positions repeatedly, or by safely retreating.
A common method for understanding the actual power of a cartridge is by comparing muzzle energies. The .30-06 Springfield, the standard caliber for American soldiers in both World Wars and a popular caliber amongst American hunters, can produce muzzle energies between 2,000 and 3,000 foot-pounds of energy (between 3 and 4 kilojoules). The .50 BMG round can produce between 10,000 and 15,000 foot pounds (between 14 and 18 kilojoules), depending on its powder and bullet type, as well as the weapon it was fired from. Due to the high ballistic coefficient of the bullet, the .50 BMG's trajectory also suffers less "drift" from cross-winds than smaller and lighter calibers, making the .50 BMG a good choice for high-powered sniper rifles.
The .50 BMG (12.7×99mm NATO) cartridge has a capacity of 290 grains H2O (19 ml). The round is a scaled-up version of the .30-06 Springfield but uses a case wall with a long taper to facilitate feeding and extraction in various weapons.
The common rifling twist rate for this cartridge is 1 in 15 in (380 mm), with 8 lands and grooves. The primer type specified for this ammunition is Boxer primer that has a single centralized ignition point (US and NATO countries). However, some other countries produce the ammunition with Berdan primers that have two flash holes.
The average chamber pressure in this round as listed in TM43-0001-27, the U.S. Army Ammunition Data Sheets — Small Caliber Ammunition, not including plastic practice, short cased spotter, or proof/test loads, is 54,923 psi (378,680 kPa). The proof/test pressure is listed as 65,000 psi (450,000 kPa).
.50 BMG cartridges are also produced commercially with a plethora of different bullets and to a number of different specifications.Cartridge, Caliber .50, Tracer, M1
Tracer for observing fire, signaling, target designation, and incendiary purposes. This bullet has a red tip.
Cartridge, Caliber .50, Incendiary, M1
This cartridge is used against unarmored, flammable targets. The incendiary bullet has a light blue tip.
Cartridge, Caliber .50, Ball, M2
This cartridge is used against personnel and unarmored targets. This bullet has an unpainted tip.
Cartridge, Caliber .50, Armor-Piercing, M2
This cartridge is used against lightly armored vehicles, protective shelters, and personnel, and can be identified by its black tip.
Cartridge, Caliber .50, Armor-Piercing-Incendiary, M8
This cartridge is used, in place of the armor-piercing round, against armored, flammable targets. The bullet has a silver tip.
Cartridge, Caliber .50, Tracer, M10
Tracer for observing fire, signaling, target designation, and incendiary purposes. Designed to be less intense than the M1 tracer, the M10 has an orange tip.
Cartridge, Caliber .50, Tracer, M17
Tracer for observing fire, signaling, target designation, and incendiary purposes. Can be fired from the M82/M107 series of rifles.
Cartridge, Caliber .50, Armor-Piercing-Incendiary-Tracer, M20
This cartridge is used, in place of the armor-piercing round, against armored, flammable targets, with a tracer element for observation purposes. This cartridge is effectively a variant of the M8 Armor-Piercing Incendiary with the added tracer element. Can be fired from the M82/M107 series of rifles. This bullet has a red tip with a ring of aluminum paint.
Cartridge, Caliber .50, Tracer, Headlight, M21
Tracer for use in observing fire during air-to-air combat. Designed to be more visible, the M21 is 3 times more brilliant than the M1 tracer.
Cartridge, Caliber .50, Incendiary, M23
This cartridge is used against unarmored, flammable targets. The tip of the bullet is painted blue with a light blue ring.
Cartridge, Caliber .50, Ball, M33
This cartridge is used against personnel and unarmored targets. Can be fired from the M82/M107 series of rifles.
Cartridge, Caliber .50, Saboted Light Armor Penetrator, M903
This cartridge has a 355 – 360 gr (23.00 – 23.33 g) heavy metal (tungsten) penetrator that is sabot-launched at a muzzle velocity of 4,000 ft/s (1,219 m/s). The 0.50 in (12.7 mm) diameter sabot is designed to separate after leaving the muzzle, releasing the 0.30 (7.62 mm) penetrator. It is injection molded of special high strength plastic and is reinforced with an aluminum insert in the base section. The cartridge is identified by an amber sabot (Ultem 1000). For use only in the M2 series of machine guns. This round can penetrate 19mm of steel armor at 1500 yards.
Cartridge, Caliber .50, Saboted Light Armor Penetrator-Tracer, M962
Like the M903, this is a Saboted Light Armor Penetrator (SLAP) round, with the only difference being that the M962 also has a tracer element for observing fire, target designation, and incendiary purposes. It uses red colored plastic sabot for identification. For use only in the M2 series of machine guns.
Cartridge, Caliber .50, Ball, XM1022
A long-range match cartridge specifically designed for long range work using the M107 rifle.
Cartridge, Caliber .50, M1022 Long Range Sniper
The .50 Caliber M1022 has an olive green bullet coating with no tip ID coloration. The projectile is of standard ball design. It is designed for long-range sniper training and tactical use against targets that do not require armor-piercing or incendiary effect. It exhibits superior long range accuracy and is trajectory matched to MK211 grade A. The M1022 is ideal for use in all .50 Caliber bolt-action and semi-automatic sniper rifles. The bullet remains supersonic out to 1,500 m (1,640 yd) to 1,600 m (1,750 yd).
Cartridge, Caliber .50, High-Explosive Armor-Piercing-Incendiary (HEIAP), Mk 211 Mod 0
A so-called "combined effects" cartridge, the Mk 211 Mod 0 High-Explosive-Incendiary-Armor-Piercing (HEIAP) cartridge contains a .30 caliber tungsten penetrator, zirconium powder, and Composition A explosive. It can be used in any .50 caliber weapon in US inventory with the exception of the M85 machine gun. Cartridge is identified by a green tip with a grey ring.
Cartridge, Caliber .50, Armor Piercing Incendiary Dim Tracer (API-DT), Mk 257
The .50 Caliber Mk 257 API-DT has a purple bullet tip. The bullet has a hardened steel core and incendiary tip. The .50 Caliber MK257 is used in machine guns M2, M3, and M85. Dim trace reduces the possibility of the weapon being located during night fire and is visible with night vision devices only.
Cartridge, Caliber .50, Armor-Piercing (AP), Mk 263 Mod 2
The .50 Caliber Mk 265 has a black tip. The bullet has a hardened steel core. It is used in machine guns M2, M3, and M85.
Cartridge, Caliber .50, Armor-Piercing-Incendiary-Tracer (API-T), Mk 300 Mod 0
As with the Mk 211 Mod 0, but with a tracer component. This cartridge likely can be used in any .50 caliber weapon in US inventory with the exception of the M85 machine gun, as with the Mk 211 Mod 0.
Cartridge, Caliber .50, Armor-Piercing-Explosive-Incendiary (APEI), Mk 169 Mod 2
This cartridge is used against hardened targets such as bunkers, for suppressive fire against lightly armored vehicles, and ground and aerial threat suppression. It is generally fired either from pilot-aimed aircraft-mounted guns or anti-aircraft platforms both produced by FN Herstal. It is identified by a gray over yellow tip. A tracer variant of it also exists.
Cartridge, Caliber .50, Ball, Mk 323 Mod 0
Created by the Naval Surface Warfare Center Crane Division, this cartridge uses M33 ball projectiles in a polymer case instead of brass. It has a clear polymer case, with a standard brass head fused at the bottom. The Mk 323 can be fired from M2HB/M2A1 machine guns and GAU-21/A aircraft guns with the same performance. It gives a 25 percent weight savings over brass-cased ammunition and allows 40 percent more ammunition to be carried for the same weight. The Mk 323's polymer casing will be applied to tracer, AP, API, and SLAP projectiles.
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.
Two distinct and non-compatible metallic links have been used for the .50 BMG cartridge, depending upon the machine gun which will be firing the cartridges. The M2 and M9 links, "pull-out" designs, are used in the Browning M2 and M3 machine guns. Pull-out cloth belts were also used at one time, but have been obsolete since 1945. The M15-series "push-through" links were used in the M85 machine gun.
The specified maximum diameter of an unfired .50 BMG bullet is 0.510-inch (13.0 mm); while this appears to be over the .50 inch (12.7 mm) maximum allowed for non-sporting Title I firearms under the U.S. National Firearms Act, the barrel of a .50 BMG rifle is only .50 inch (12.7 mm) across the rifling lands and slightly larger in the grooves. The oversized bullet is formed to the bore size upon firing, forming a tight seal and engaging the rifling, a mechanism which in firearms terms is known as engraving. Subject to political controversy due to the great power of the cartridge (it is the most powerful commonly available cartridge not considered a destructive device under the National Firearms Act), it remains popular among long-range shooters for its accuracy and external ballistics. While the .50 BMG round is able to deliver accurate shot placement (if match grade ammunition is used) at ranges over 1,000-yard (910 m), smaller caliber rifles produce better scores and tighter groups in 1,000-yard (910 m) competitions.
In response to legal action against the .50 BMG in the United States and Europe, an alternative chambering was developed. The .510 DTC Europ uses the same bullet, but has slightly different case dimensions. .510 DTC cases can be made by fire-forming .50 BMG cases in a .510 DTC chambered rifle. The new round has almost identical ballistics, but because of the different dimensions, rifles chambered for .50 BMG cannot fire the .510 DTC, and therefore rifles chambered for .510 DTC do not fall under many of the same legal prohibitions. Barrett offers a similar alternative, the .416 Barrett, which is based on a shortened .50 BMG case necked down to .416 caliber (10.3 mm).
A 1999 Justice Department Office of Special Investigations briefing on .50 caliber rifle crime identified several instances of the .50 BMG being involved in criminal activities. Most of the instances of criminal activity cited in the Office of Special Investigations briefing involved the illegal possession of a .50 BMG rifle. The briefing did not identify any instance of a .50 BMG rifle being used in the commission of a murder.
Within the United Kingdom, it is legal to own a .50 BMG rifle with a section 1 Firearms Certificate. Applications requesting firearms in this caliber are not subject to any extra scrutiny compared to smaller calibers.
There have been persistent reports of a belief among some members of the United States Armed Forces that the use of .50 BMG in a direct antipersonnel role is somehow prohibited by the laws of war. This is incorrect and has been characterized as a myth; writing for the Marine Corps Gazette, Maj. Hays Parks states that "No treaty language exists (either generally or specifically) to support a limitation on [the use of .50 BMG] against personnel, and its widespread, longstanding use in this role suggests that such antipersonnel employment is the customary practice of nations." Parks theorizes that the myth originated in historical doctrine discouraging the use of the M8C spotting rifle—an integral .50-caliber aiming aid for the M40 recoilless rifle—in the antipersonnel role. This limitation was entirely tactical in nature, having been intended to help conceal the vulnerable M40 and its crew from the enemy before the main anti-tank gun could be fired, but some personnel may have erroneously assumed the existence of a legal limitation on the use of .50-caliber projectiles more generally.
The primary military use of this round is in the Browning M2HB heavy machine gun.
The U.S. Coast Guard uses .50 BMG rifles to disable outboard engines from armed helicopters during interdictions. Similarly, .50 BMG weapons have attracted attention from law enforcement agencies; they have been adopted by the New York City Police Department as well as the Pittsburgh Police. A .50 BMG round can effectively disable a vehicle when fired into the engine block. If it is necessary to breach barriers, a .50 BMG round will penetrate most commercial brick walls and concrete cinder blocks.
The .50 BMG round has been used as a sniper round as early as the Korean War. The 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); 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.
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. (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.)
In addition to long-range and anti-materiel sniping, the U.S. military uses .50 BMG weapons to detonate unexploded ordnance from a safe distance. It can disable most unarmored and lightly armored vehicles.
Some civilians use .50 caliber rifles for long-range target shooting: the US-based Fifty Caliber Shooters Association holds .50 BMG shooting matches.Barrett M82CQ (a carbine version of the M82A3)
Bushmaster BA50 carbine (22" barrel version of the BA50)
Accuracy International AS50
Accuracy International AW50
Arms Tech Ltd. TTR-50
EDM Arms Windrunner
Gepard anti-materiel rifle
L.A.R. Manufacturing, Inc. Grizzly Big Boar
OM 50 Nemesis
PGM Hecate II
Pindad SPR-2 and Pindad SPR-3
Serbu Firearms BFG-50 (single-shot bolt-action) and BFG-50A (semi-automatic)
Steyr HS .50
Zastava M93 Black Arrow
CS/LM5 Gatling machine gun
M2 Browning machine gun
M85 machine gun
MAC-58 - did not enter production
Rolls-Royce Experimental Machine Gun - only built as prototype
W95 HMG (Type 85 HMG Export)