.50 BMG
The .50 Browning Machine Gun (.50 BMG, 12.7×99mm NATO and designated as the 50 Browning by the C.I.P.) is a caliber cartridge developed for the M2 Browning heavy machine gun in the late 1910s, entering official service in 1921. Under STANAG 4383, it is a standard service cartridge for NATO forces as well as many non-NATO countries. The cartridge itself has been made in many variants: multiple generations of regular ball, tracer, armor-piercing (AP), incendiary, and saboted sub-caliber rounds. The rounds intended for machine guns are made into a continuous belt using metallic links . The .50 BMG cartridge is also used in anti-materiel rifles. 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. History. In response to the need for new anti-aircraft weaponry during World War I, John Browning developed the .50 BMG. He wanted the round to be used in a machine gun, and wanted the machine gun to be based on a scaled-up version of the M1917 Browning. 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 and against aircraft. According to the "American Rifleman": "Actually, the Browning .50 originated in the Great War. American interest in an armor-piercing cartridge was influenced by the marginal French 11 mm design, prompting U.S. Army Ordnance officers to consult Browning. They wanted a heavy projectile at 2700 feet per second (f.p.s.), but the ammunition did not exist. Browning pondered the situation and, according to his son John, replied, 'Well, the cartridge sounds pretty good to start . You make up some cartridges and we'll do some shooting.'" The "American Rifleman" further explains that development was "[r]eputedly influenced by Germany's 13.2x92 mm SR (.53-cal.) anti-tank rifle" and that then "Ordnance contracted with Winchester to design a .50-cal. cartridge. Subsequently, Frankford Arsenal took over from Winchester, producing the historic .50 BMG or 12.7x99 mm cartridge. The Army then returned to John Browning for the actual gun. Teamed with Colt, he produced prototypes ready for testing and, ironically, completed them by Nov. 11, 1918—the Great War's end." The round was put into use  in the M1921 Browning machine gun. This gun was later developed into the M2HB Browning which with its .50 caliber armor-piercing cartridges went on to function as an anti-aircraft and anti-vehicular machine gun, capable of penetrating of face-hardened armor steel plate at , of rolled homogeneous armor at the same range, and at . 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, restricting the destructive capability of the M2. 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 armored  vehicles mount 12.7×108mm NSVs, which have similar dimensions to .50 BMGs). Decades later, the .50 BMG was chambered in high-powered rifles as well. 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 (over one mile) between firing position and target allows time for the sniper to avoid enemy retaliation by either changing positions repeatedly, or by safely retreating . Typical uses. The primary military use of this round is in the Browning M2HB heavy machine gun and the Barrett M82 anti-materiel rifle. 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 during the Vietnam War, at a distance of ; 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. In June 2017, a McMillan Tac-50 was used by a sniper with Canada's Joint Task  Force 2 to kill an Islamic State insurgent in Iraq, setting the world record for the longest confirmed kill shot in military history at . Before that record, Canadian Army Corporal Rob Furlong of the PPCLI achieved what was then the longest-range confirmed sniper kill in history when he shot a Taliban combatant at during the 2002 campaign in the Afghanistan War. This was surpassed in 2009 by a British sniper in Afghanistan with 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. Power. A common method for understanding the actual power of a cartridge is comparison of 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 . The .50 BMG round can produce between , depending on its powder and bullet type, as well as the weapon  it is 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. Cartridge dimensions. The .50 BMG (12.7×99mm NATO) cartridge has a capacity of . 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 , with eight lands and grooves . The primer type specified for this ammunition is a 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 . The proof/test pressure is listed as . Military cartridge types. The .50 BMG cartridge is also produced commercially in a wide range of specifications, including armor piercing, tracing, and  incendiary. DARPA (Defense Advanced Research Projects Agency) contracted with Teledyne Scientific Company to develop the EXACTO program, including a .50-caliber guided bullet. Videos published by DARPA show the guided bullet diverting to strike a moving target. Belt links. Three distinct and non-compatible metallic links have been used for .50 BMG cartridge belts. The M2 and M9 links, "pull-out" designs, are used in the Browning M2 and M3 machine guns. The M15-series metal "push-through" links were used in the M85 machine gun. Pull-out cloth belts were also used at one time, but have been obsolete  since 1945. Legal issues. The specified maximum diameter of an unfired .50 BMG bullet is ; 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 firearm terms is known as swaging. 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 , smaller caliber rifles produce better scores and tighter groups in competitions. 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. In the United States, Washington, D.C. disallows  registration of .50 BMG rifles, thus rendering civilian possession unlawful. California prohibits the private purchase of a rifle capable of firing the .50 BMG through the .50 Caliber BMG Regulation Act of 2004. Connecticut specifically bans the Barrett 82A1 .50 BMG rifle. However, .50 BMG rifles registered prior to the enacted bans remain lawful to possess in California and Connecticut. Maryland imposes additional regulations on the sale and transfer of .50 BMG rifles and other "regulated firearms", and limits purchases of any firearm within this class to one per month, but does not impose registration requirements or any form of  categorical ban. Within the United Kingdom, it is legal to own a bolt action .50 BMG rifle with a section 1 Firearms Certificate. Applications requesting firearms in this caliber are assessed by the same criteria as smaller calibers; with the applicant having to prove they have a valid reason for owning such a weapon. Contrary to a persistent misconception within the United States Armed Forces, using .50 BMG directly against enemy personnel is not prohibited by the laws of war. 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 misconception 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 and was intended to hide the vulnerable M40 and its crew from the enemy until the main anti-tank gun was ready for firing; however, Parks concludes that some U.S. troops  assumed the existence of a legal limitation on the use of .50-caliber projectiles more generally.