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From left: .50 BMG, 300 Win Mag, .308 Winchester, 7.62 Soviet, 5.56 NATO, .22LR
|Place of origin||United States|
|In service||1914 to present|
|Used by||United States Military|
|Wars||WWI and WWII|
|Bullet diameter||.511 in (12.98 mm)|
|Neck diameter||.560 in (14.22 mm)|
|Shoulder diameter||.741 in (18.82 mm)|
|Base diameter||.804 in (20.42 mm)|
|Rim diameter||.804 in (20.42 mm)|
|Case length||3.91 in (99.31 mm)|
|Overall length||5.45 in (138.43 mm)|
|Filling weight||289 gr. (water)|
|647 gr Speer||3044 ft/s
|655 gr ADI||3029 ft/s
|700 gr Barnes||2978 ft/s
|750 gr Lapua||2618 ft/s
|800 gr Barnes||2895 ft/s
Test barrel length: 45 in
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 greatly 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. 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 machine guns. The use in single-shot and semi-automatic rifles has resulted in many specialized match-grade rounds not used in .50 machine guns. A .50BMG sniper rifle by McMillan was used by Canadian Corporal Rob Furlong to bring off the longest-range confirmed sniper kill in history, when he shot a Taliban insurgent at 2,430 metres (1.51 miles) during the 2002 campaign in Afghanistan.
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.
The round was conceptualized during WW1 by John Browning in response to a requirement for an anti-aircraft weapon. The round itself is based on a scaled-up .30-06 Springfield design, and the machine gun was based on a scaled-up M1919/M1917 design that Browning had initially developed at the turn of century (but which was not adopted by the U.S. military until 1917, hence the model designation). The new heavy machine gun, the Browning M2 .50 caliber machine gun, was used heavily in aircraft, especially during World War II, though its airborne use is limited to helicopters at present. It was and still is used on the ground as well, both vehicle mounted, in fixed fortifications and on occasion carried by infantry. The incendiary rounds were especially good against aircraft, and AP rounds for destroying concrete bunkers, structures, and lighter AFVs.
The development of the .50 round is sometimes confused with the German 13 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 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. However, after some analysis the German ammunition was ruled out, both because performance was inferior to the modified Springfield .30-06 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 different. The M2 would, however, go on to function as an anti-armour machine gun, and decades later, be used in high-powered rifles. The concept of a .50 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 machine guns such as the Gatling.
During World War II it found use in penetrating lightly armoured vehicles, including aircraft. An upgraded variant of the Browning machine gun used during World War 2 is still in use today as the well known M2 machine gun. Since the mid-1950s, some armoured 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 light machine guns such as general purpose machine guns, but is difficult to maintain and aim in field conditions. Its range and accuracy, however, are superior to light machine guns when fixed and water cooled, and has not been replaced as the standard caliber for western vehicle mounted machine guns (Soviet and CIS armoured vehicles mount 12.7 mm DShK, NSV, which are ballistically very similar to the .50 BMG, or 14.5 mm KPV machine guns, which have significantly superior armour penetration compared to any 12.7 mm round).
The Barrett M82 .50 Caliber rifle and later variants were born during the 1980s and have upgraded the anti-material power of the military sniper. A skilled sniper can effectively neutralize an infantry unit by picking off several soldiers at a very long range, without revealing his precise location, then spend a few hours moving to a new position (whether the infantry unit decides to hunt down the sniper or to retreat), before firing again. However, due to the great destructive power of the ammunition, such heavy-caliber sniper rifles are considered anti-material weapons.
A common method for understanding the actual power of a cartridge is by comparing muzzle energies. The Springfield .30-06, the standard caliber for American soldiers in World War II and a popular caliber amongst American hunters, can produce muzzle energies between 2000 and 3000 foot pounds of energy (between 2711 and 4067 joules). A .50 BMG round can produce between 10,000 and 13,000 foot pounds (between 13558 and 17625 joules) or more, depending on its powder and bullet type, as well as the rifle 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.
 US Military Cartridge Types
NOTE: .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. The M1 has a red tip.
- Cartridge, Caliber .50, Incendiary, M1
- This cartridge is used against unarmored, flammable targets. The tip of the bullet is painted a light blue.
- Cartridge, Caliber .50, Ball, M2
- This cartridge is used against personnel and unarmored targets.
- 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 bullet tip.
- Cartridge, Caliber .50, Armor-Piercing-Incendiary, M8
- This cartridge is used, in place of the armor piercing round, against armored, flammable targets. The tip of the bullet is colored with aluminum paint.
- Cartridge, Caliber .50, Tracer, M10
- Tracer for observing fire, signaling, target designation, and incendiary purposes. Designed to be less intense than the M1, 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. The tip of the bullet is colored red with a ring of aluminum paint. 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.
- 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 is a Saboted Light Armor Penetrator (SLAP) round, which uses a smaller 355-360 grain bullet fitted in an amber colored plastic sabot. For use only in the M2 series of machine guns.
- 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. Uses a red colored plastic sabot for indentification. 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.
- 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. Cartridge is identified by a green tip with a grey ring, and can be used in any .50 caliber weapon in US inventory with the exception of the M85 machine gun.
 Legal issues
The specified maximum diameter of an unfired .50 BMG bullet is .510 inch; while this appears to be over the .50 inch (12.7 mm) maximum allowed for non-sporting Title I small arms under the U.S. National Firearms Act, the barrel of a .50 BMG rifle is only .50 inches 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 yards (900 m), smaller caliber rifles produce better scores and tighter groups in 1000 yard competitions.
Since the adoption of .50 BMG rifles by military sniper units, there has been a growing gun control movement in some states, including California, New York, Massachusetts, Hawaii, and Illinois, to ban civilian possession of .50 BMG rifles and ammunition. Bill AB50 in California, passed in 2004, classifies all .50 BMG rifles of any action type as assault weapons, which are illegal to import into the state or transfer to any but a state agency or dealer licensed to purchase them. The bill's sponsor, California Assemblyman Paul Koretz, claimed that the .50 BMG "would be an ideal choice for use in an act of terrorism," it is considered by gun experts to be a poor choice because of it's size, weight and cost. The considerable size and weight of .50 BMG rifles, high cost (many manufactures offer them for under USD$2,200 ), and lack of concealibility make them a poor choice for criminal use. With lengths usually between four and five feet and weighing 20-35 pounds, they are unwieldy and difficult to conceal.
After AB50 was passed, Barrett proceeded to cease sales and service of .50 BMG rifles to California law enforcement agencies. An official press release from the owner of Barrett Firearms can be found on the company's website, as follows: "The California legislature has banned the .50 BMG from the good citizens of the state of California, violating their rights and the constitution of our republic. Therefore, Barrett will not sell to or service any California government agencies."
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-forging .50 BMG cases. The new round has almost identical ballistics, but because of the different dimensions, rifles chambered for the .50 BMG cannot fire the .510 DTC, and vice versa, and therefore 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).
The primary civilian users of .50 caliber rifles, which range in price from around $US1,800 for single shot models to nearly US$8000 for the Barrett M82A1, are long-range target shooters; the Fifty Caliber Shooters Association, for instance, holds .50 BMG shooting matches nationwide.