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 The M2 machine gun or Browning .50 caliber machine gun (informally, "Ma Deuce") is a heavy machine gun that was designed towards the end of World War I by John Browning John Moses Browning (January 23, 1855 – November 26, 1926) was an ...

heavy machine gun A heavy machine gun (HMG) is significantly larger than light Light or visible light is electromagnetic radiation In physics Physics is the natural science that studies matter, its fundamental constituents, its motion a ...

in the late 1910s, entering official service in 1921. Under STANAG 4383, it is a standard service cartridge for

NATO The North Atlantic Treaty Organization (NATO, ; french: Organisation du traité de l'Atlantique nord, ), also called the North Atlantic Alliance, is an intergovernmental military alliance between 30 member states – 28 European and two N ...

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 gun A machine gun is a fully automatic, rifled autoloading firearm A firearm is any type of gun designed to be readily carried and used by an individual. The term is legally defined further in different countries (see Legal definitions). ...

s 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 Ammunition (informally ammo) is the material fired, scattered, dropped, or detonated from any weapon or weapon system. Ammunition is both expendable weapons (e.g., bombs, missiles, grenades, land mines) and the component parts of other weapo ...

is available, and the availability of

match grade Match grade frequently refers to quality firearm parts and ammunition that are suitable for a competitive match. Sometimes it also refers to other devices and parts that are made with high precision in mind. Description In firearm A firearm ...

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 World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe Europe is a large peninsula conventionally considered a continent in ...

John Browning John Moses Browning (January 23, 1855 – November 26, 1926) was an American firearm designer who developed many varieties of military and civilian firearms, cartridges, and gun mechanisms many of which are still in use around the world. He ...

developed the .50 BMG. He wanted the round to be used in a

, 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 An anti-tank rifle is an anti-materiel rifle designed to penetrate the armor of armored fighting vehicles, most commonly tanks, armored personnel carrier An armoured personnel carrier (APC) is a broad type of armoured military vehicle de ...

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.'"Barrett Tillman, American Rifleman,February 23, 2017, https://www.americanrifleman.org/articles/2017/2/23/the-50-cal-browning-machine-gun-the-gun-that-won-the-war/ The ''American Rifleman'' further explains that development was " putedly 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 Rolled homogeneous armour (RHA) is a type of vehicle armour Military vehicles are commonly armour Armour (British English British English (BrE, en-GB, or BE) is, according to Oxford Dictionaries, " English as used in Great Brita ...

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 gun A general-purpose machine gun (GPMG) is an air-cooled, usually belt-fed machine gun A machine gun is a fully automatic, rifled autoloading firearm A firearm is any type of gun designed to be readily carried and used by an individ ...

s, though it is significantly heavier and more cumbersome to transport. Its range and accuracy, however, are superior to

light machine gun A light machine gun (LMG) is a light-weight machine gun designed to be operated by a single infantryman, with or without an assistant, as an infantry support weapon. LMGs firing cartridges of the same caliber as the other riflemen of th ...

s 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 rifle was developed during the 1980s and, along with later variants, has upgraded the anti-

materiel Materiel (; ) refers to supplies, equipment, and weapons in military supply-chain management, and typically supplies and equipment in a commercial supply chain context. In a military context, the term ''materiel'' refers either to the spe ...

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 M2 Browning machine gun and anti-materiel rifles such as the Barrett M82. 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 The New York City Police Department (NYPD), officially the City of New York Police Department, established on May 23, 1845, is the primary municipal law enforcement agency within the New York City, City of New York, the largest and one of ...

as well as the Pittsburgh Police. A .50 BMG round can effectively disable a vehicle when fired into the

engine block In an internal combustion engine, the engine block is the structure which contains the cylinders and other components. In an early automotive engine, the engine block consisted of just the cylinder block, to which a separate crankcase was att ...

. A .50 BMG round will penetrate most commercial brick walls and concrete cinder blocks. The .50 BMG round was used as a sniper round as early as the

Korean War {{Infobox military conflict , conflict = Korean War , partof = the Cold War The Cold War is a term commonly used to refer to a period of Geopolitics, geopolitical tension between the United States and the Soviet ...

. The former record for a confirmed long-distance kill was set by U.S. Marine sniper Carlos Hathcock in 1967 during the

Vietnam War The Vietnam War (also known by other names) was a conflict in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. It was the second of the Indochina Wars and was officially fought between North Vie ...

, at a distance of ; Hathcock used the .50 BMG in an M2 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 new world record for the longest confirmed kill shot in military history at . Before that, a British sniper in Afghanistan held the record at using a .338 Lapua Magnum (8.58×70 mm) rifle. In addition to long-range and anti-materiel, 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 In ballistics Ballistics is the field of mechanics concerned with the launching, flight Flight or flying is the process by which an object moves through a space without contacting any planetary surface, either within an atmosphere (i ...

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 In firearm A firearm is any type of gun designed to be readily carried and used by an individual. The term is legally defined further in different countries (see Legal definitions). The first firearms originated in 10th-century China ...

twist rate In firearm A firearm is any type of gun designed to be readily carried and used by an individual. The term is legally defined further in different countries (see Legal definitions). The first firearms originated in 10th-century China ...

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. ; Cartridge, caliber .50, tracer, M1 : This tracer is used 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 (AP), 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 (API), 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 (API-T), 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 three 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 (SLAP), 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 in (7.62 mm) penetrator. The sabot 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). Used only in the M2 series of machine guns. This round can penetrate 0.75 in (19 mm) of steel armor at . ; Cartridge, caliber .50, saboted light armor penetrator tracer (SLAP-T), M962 : Like the M903, this is a SLAP round, with the only difference being that the M962 also has a tracer element for observing fire, target designation, and incendiary purposes. It has a red plastic sabot for identification, and is used 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 effects. 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 from to . ; Cartridge, caliber .50, high-explosive incendiary armor-piercing (HEIAP), Mk 211 Mod 0 : A "combined effects" cartridge, the Raufoss Mk 211 Mod 0 HEIAP cartridge contains a .30 caliber tungsten penetrator, zirconium powder, and Composition A explosive. It can be used in any .50 caliber weapon in the US inventory with the exception of the M85 machine gun. The cartridge is identified by a green tip with a gray 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. It is used in the M2, M3, and M85. Dim trace reduces the possibility of the weapon being located during night fire and is visible only with night-vision devices. ; Cartridge, caliber .50, armor-piercing (AP), Mk 263 Mod 2 : The .50 caliber Mk 263 has a black tip. The bullet has a hardened steel core and features double valleys to reduce bearing surface thereby decreasing friction and increasing stability. It is used in the 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 the 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 Fabrique Nationale Herstal (), trading as FN Herstal and often referred to as Fabrique Nationale or simply FN, is a leading firearm A firearm is any type of gun designed to be readily carried and used by an individual. The term is legally d ...

. 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 polymer cases 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 is applied to tracer, AP, API, and SLAP projectiles.

DARPA The Defense Advanced Research Projects Agency (DARPA) is a research and development Research and development (R&D or R+D), known in Europe Europe is a large peninsula conventionally considered a continent in its own right because ...

(Defense Advanced Research Projects Agency) contracted with Teledyne Scientific Company to develop the

EXACTO EXACTO, an acronym An acronym is a word or name formed from the initial components of a longer name or phrase. Acronyms are usually formed from the initial letters of words, as in '' NATO'' (''North Atlantic Treaty Organization''), but som ...

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. File:M2 M9 links.gif, M2 and M9 links File:M15A2 link.gif, M15A2 link File:Defense.gov photo essay 120814-F-QT695-001.jpg, M9 links in use

Legal issues

United Kingdom

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.

United States

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 National Firearms Act (NFA), 73rd Congress, Sess. 2, ch. 757, was enacted on June 26, 1934, and currently codified and amended as . The law is an Act of Congress in the United States The United States of America (U.S.A. or USA), c ...

, the barrel of a .50 BMG rifle is only .50 inch (12.7 mm) across the

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. 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 In the United States, a destructive device is a type of firearm or explosive device regulated by the National Firearms Act of 1934, revised by the Omnibus Crime Control and Safe Streets Act of 1968 and Gun Control Act of 1968. Examples of destr ...

under the National Firearms Act), it remains popular among long-range shooters for its accuracy and

external ballistics External ballistics or exterior ballistics is the part of ballistics Ballistics is the field of mechanics concerned with the launching, flight Flight or flying is the process by which an object moves through a space without contacting ...

. While the .50 BMG round is able to deliver accurate shot placement (if

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 California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

prohibits the private purchase of a rifle capable of firing the .50 BMG through the .50 Caliber BMG Regulation Act of 2004.

Connecticut Connecticut () is the southernmost state in the New England region of the Northeastern United States. It is bordered by Rhode Island to the east, Massachusetts to the north, New York to the west, and Long Island Sound to the south. Its ...

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 Maryland ( ) is a state in the Mid-Atlantic region of the United States. It shares borders with Virginia Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United S ...

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. Contrary to a persistent misconception within the

United States Armed Forces The United States Armed Forces are the military forces of the United States. The armed forces consists of six service branches: the Army, Marine Corps, Navy, Air Force, Space Force, and Coast Guard. The president of the United States ...

, using .50 BMG directly against enemy personnel is not prohibited by the

laws of war The law of war is the component of international law that regulates the conditions for initiating war ('' jus ad bellum'') and the conduct of warring parties (''jus in bello''). Laws of war define sovereignty and nationhood, states and terri ...

. Writing for the ''

Marine Corps Gazette ''Marine Corps Gazette'' is a professional journal for U.S. Marines founded in 1916 at Marine Corps Base Quantico for members of the United States Marine Corps The United States Marine Corps (USMC), also referred to as the United States Marin ...

'', Maj Hays Parks states that "No treaty language exists (either generally or specifically) to support a limitation on he use of .50 BMGagainst 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 Anti-tank warfare originated from the need to develop technology and tactics to destroy tanks during World War I. Since the Triple Entente deployed the first tanks in 1916, the German Empire developed the first anti-tank weapons. The first ...

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.

Partial list of .50 BMG firearms

Carbines

* Barrett M82CQ (a carbine version of the M82A3) * Bushmaster BA50 carbine (22" barrel version of the BA50) * Serbu Firearms BFG-50 Carbine (22" barrel version of the BFG-50 single-shot bolt-action)

Rifles

* Accuracy International AS50 * Accuracy International AW50 * Accuracy International AX50 * ArmaLite AR-50 * Arms Tech Ltd. TTR-50 * Barrett M82/M107 * Barrett M95 * Barrett M99 * Bushmaster BA50 * Cadex Defence CDX-50 Tremor * Desert Tech HTI * DSR-50 * Gepárd anti-materiel rifle * McMillan TAC-50 * OM 50 Nemesis * PGM Hécate II * Pindad SPR-2 * Ramo M600 * Robar RC-50 * Serbu Firearms BFG-50 (single-shot bolt-action) * Serbu Firearms BFG-50a (magazine fed semi-automatic) * Serbu Firearms RN-50 (single-shot modified break-action) * Snipex M * Snipex Rhino Hunter * Steyr HS .50 * WKW Wilk *

Zastava M93 Black Arrow The M93 Black Arrow ( sr, М93 Црна стрела/''M93 Crna strela'') is a 12.7×108mm anti-materiel rifle developed and manufactured by Zastava Arms. Overview The rifle was designed in 1993 and entered production in 1998. The primary purp ...

Machine guns

GAU-19 The GAU-19/A (GECAL 50) is an electrically driven, three-barrel rotary heavy machine gun A heavy machine gun (HMG) is significantly larger than light Light or visible light is electromagnetic radiation In physics Physi ...

* M1921 Browning machine gun *

M2 Browning machine gun The M2 machine gun or Browning .50 caliber machine gun (informally, "Ma Deuce") is a heavy machine gun A heavy machine gun (HMG) is significantly larger than light Light or visible light is electromagnetic radiation In physics ...

* M85 machine gun * Rolls-Royce Experimental Machine Gun - only built as prototype * STK 50MG * XM218 *

XM312 The XM312 is a heavy machine gun A heavy machine gun (HMG) is significantly larger than light Light or visible light is electromagnetic radiation In physics Physics is the natural science that studies matter, its fund ...

* XM806 (LW50) *

Kord machine gun The Kord-12.7 mm heavy machine gun A heavy machine gun (HMG) is significantly larger than light Light or visible light is electromagnetic radiation In physics Physics is the natural science that studies matter, it ...

- export variant

Pistols

* Triple Action Thunder

Chain gun

* Profense PF 50

References

{{Current Indian infantry weapons

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 The M2 machine gun or Browning .50 caliber machine gun (informally, "Ma Deuce") ...

NATO cartridges Weapons and ammunition introduced in 1921 Winchester Repeating Arms Company cartridges