This article is about the .50 caliber M2 machine gun. For the .30-06 M2 machine gun, see M1919 Browning.

The M2 Machine Gun (Browning .50 Caliber Machine Gun, Ma Deuce) is a heavy machine gun designed towards the end of World War I by John Browning. It was nicknamed Ma Deuce by US troops (because "she always has the last word") or simply called "fifty-cal" in reference to its caliber. The design has had many specific designations; the official designation for the infantry type is Browning Machine Gun, Cal. .50, M2, HB, Flexible.

The M2 has been used extensively as a vehicle weapon and for aircraft armament by the United States from 1933 to the present day. It was heavily used during World War II, the Korean War, the Vietnam War, as well as during operations in Iraq in the 1990s and 2000s. It is the primary heavy machine gun of NATO countries, and has been used by many other countries. It is still in use today, and is the second longest-serving weapon in the US arsenal, after the M1911 pistol.


The development of the Browning M2 was a direct response to the appearance of the Junkers J.I in 1917, an all-metal aircraft with a steel "bathtub" to protect the pilot, which proved immune to existing rifle rounds. Fearing future developments, General Pershing ordered development of a new machine gun with a caliber not less than .5 inches and a muzzle velocity not less than 2,700 feet pet second. John Moses Browning promptly set about redesigning his M1919 machine gun to meet this requirement, while a team at Winchester set about enlarging their .30-06 Springfield round to match it. The final work by Winchester was based on the .525 TuF round fired by the Mauser 1918 T-Gewehr, several captured examples of which had been sent to them.

Browning presented the result in two variants, the air-cooled M1918 prototype and the water-cooled M1921 for Navy use. These variants fed from the left and ejected to the right, and were sufficiently troublesome that they were not adopted in quantity.

In 1926 following Browning's death, a Dr. S. H. Green picked up development, redesigning the M1921 with a downward-ejecting common receiver which could feed from either side and featured a reversible charging handle. He created seven different gun configurations for various services and applications, with the US Navy picking up the water-cooled variant in 1933 and the Army adopting the air-cooled heavy barrel version (M2HB) shortly after. The Air Force adopted a faster-firing air-cooled version, the M2 Aircraft or AN/M2.

Due to the long procedure for changing the barrel, an improved system was developed called QCB (quick change barrel). A lightweight version, weighing 24 lb (11 kg) less—a mere 60 lb (27 kg)—was also developed.

The M2 has thus far resisted all attempts to replace it: the late 50s M85 proved overcomplicated and unreliable and was ultimately retired in the 80s with all mountings either removed or swapped for M2s. The later XM307 ACSW and XM312 were cancelled in 2008 after failing to meet rate-of-fire and weight goals, as was their successor the XM806 in 2012 for again failing the rate of fire goal, with the only surviving part of those programs being the lightweight M205 tripod.


The M2 is a scaled-up version of John Browning's M1919 .30 caliber machine gun (until the adoption of the M2A1 in 2010 even using the same timing gauges), and fires the .50 BMG cartridge. The M2 is an air-cooled, belt-fed machine gun that fires from a closed bolt (unusual for a machine gun), operated on the short recoil principle. In this action, the bolt and barrel are initially locked together, and recoil upon firing. After a short distance, the bolt and barrel unlock, and the bolt continues to move rearwards relative to the barrel. This action opens the bolt, and pulls the belt of ammunition through the weapon, readying it to fire again, all at a cyclic rate of 450-550 rounds per minute. This is a rate of fire not generally achieved in use, as sustained fire at that rate will "shoot out" the barrel within a few thousand rounds, necessitating replacement. The M2 machine gun's sustained rate of fire is considered to be anything less than 40 rounds per minute.

The M2 has an absolute maximum range of 7.4 kilometers (4.2 miles) when using the M2 ball ammunition, with a maximum effective range of 1.8 kilometers (1.2 miles) when fired from the M3 tripod. In its ground-portable, crew-served role, the gun itself weighs in at a hefty 84 pounds (38 kg), and the assembled M3 tripod another 44 pounds (20 kg). Each belt box is also fairly hefty, with the WW2-era 105-round M2 box weighing 35 pounds (15.9 kg) when full. In this configuration, the butterfly trigger is located at the very rear of the weapon, with spade grips on either side of it and the bolt release in the center. The spade grips are gripped and the trigger is depressed with one or both thumbs. When the bolt release is in the up position, the weapon is in single-shot mode. The bolt release must be pressed each time the weapon is fired to close the bolt and reload the weapon. The bolt release can be locked into the down position resulting in fully-automatic firing.

Because the M2 was designed with intent in many configurations, it can be adapted to feed in rounds from the left or right side of the weapon by exchanging the belt-holding pawls, the belt feed pawl, the front and rear cartridge stops and reversing the bolt switch. The conversion can be completed within a minute with no tools.

When firing blanks, a large blank-firing adapter (BFA) must be used, in order to keep the gas pressure high enough to allow the action to cycle. It is very distinctive, with attachment to the muzzle and three rods extending back to the base. The BFA can often be seen on M2s in peacetime operations. For a most of the gun's service life there was no standard BFA for the M2, forcing units to build their own for training: a 1976 report from the Defense Technical Information Center found these devices tended to damage the weapons they were attached to.[1]

Combat usageEdit

The M2 .50 Browning machine gun has been used for various roles:

  • An infantry support weapon
  • When doubled it is used as an anti-aircraft gun in some ships, or on the ground. In these cases a pair of one left-handed and one right-handed feeds are used. In some cases up to six guns (usually four) are mounted. All anti-aircraft use was recognised as obsolete in WW2, though the towed M45 Quadmount was not directly replaced until the adoption of the M167 Vulcan Air Defense System in 1967.
  • Primary or secondary weapon on an armored fighting vehicle or military truck
  • Primary or secondary weapon on a naval patrol boat
  • Secondary weapon for anti-boat defense on larger surface warships
  • Coaxial gun or hatch mounting in some tanks
  • A primary armament in WWII-era U.S. aircraft such as the P-51 Mustang, and the Korean-era U.S. F-86 Sabre.
  • Defensive armament in WWII-era bombers like the B-17 Flying Fortress and B-24 Liberator.
  • A long range sniper rifle, when attached with a scope. One well-known expert was US Marine sniper Carlos Hathcock during the Vietnam War. The success of the M2 in this role led to the development of actual sniper rifles based on the same .50 caliber round.

Commonwealth use of the .50 was limited in the Second World War, despite it being standard armament on US-built/designed AFVs such as the M4 Sherman or M10 Wolverine that began to see use in British, Canadian, Australian and New Zealand units from 1942 on. Commonwealth tank crew commanders more often than not deleted the .50 altogether as being of limited use, given several factors. Primarily, the weapon was an anti-aircraft weapon (though it proved quite capable of damaging Japanese tanks in the Pacific), and Allied aerial superiority precluded its necessity. The weapon also could not be easily employed while under fire without risking the death of the commander. Commanders - especially in Italy - also found that the gun caught on low-hanging trees and vines and posed a danger to the crew commander's head and face if it whipped around.

Variants and derivativesEdit

Twin .50 caliber machine gun

Modern aircooled naval twin-mounting

M2 VariantsEdit

The basic M2 was deployed in US service in a number of subvariants, all with separate complete designations as per the US Army system. The basic designation as mentioned in the introduction is Browning Machine Gun, Cal. .50, M2, with others as described below.

The water-cooled variants adopted by the US Navy for anti-aircraft use were designated Browning Machine Gun, Cal. .50, M2, Water-Cooled, Flexible. There was no fixed water-cooled version. This variant was obsolete by the start of WW2 and was replaced on Navy ships by the Oerlikon 20mm Cannon on a one-to-one or better ratio starting in 1941.

Air-cooled heavy barrel versions came in three subtypes. The basic infantry model, Browning Machine Gun, Cal. .50, M2, HB, Flexible, a fixed developed for use on the M6 Heavy Tank designated Browning Machine Gun, Cal. .50, M2, HB, Fixed, and a "turret type" whereby "Flexible" M2s were modified slightly for use in tank turrets. The subvariant designation Browning Machine Gun, Cal. .50, M2, HB, Turret was only used for manufacturing, supply, and administration identification and separation from flexible M2s.

Specific aircraft versions were also developed, and these subvariants are discussed in the following paragraph along with the AN/M2.

M2 machine gun

AN/M2, M3, XM296/M296, and GAU-10/AEdit

The M2 machine gun was heavily used as a remote fired fixed weapon, primarily in aircraft, but also in other applications. For this a variant of the M2 was developed (sometimes seen under the designation AN/M2, but it is important to note that there were .30 and .50 caliber weapons with this designation), with the ability to fire from a solenoid trigger. For aircraft mounting some were also fitted with substantially lighter barrels, permitted by the cooling effect of air in the slip-stream. The official designation for this weapon was Browning Machine Gun, Aircraft, Cal. .50, M2 followed by either "Fixed" or Flexible" depending on whether the weapon was used as a fixed forward firing gun or for use by an airplane's crew, such as a waist gun position on a B-17.

The M3 or AN/M3 was a more purpose-built variant for remote firing use, often fitted with a self-cocking mechanism and with the rate of fire either electrically or mechanically boosted to 1,150-1,250 rpm. It was the last incarnation of the M2 to serve as armament for fixed-wing fighter aircraft.

The XM296/M296 is a further development of the M2/M3 machine gun for remote firing applications, and is currently used in armament systems pertaining to the OH-58 Kiowa Warrior helicopter. The M296 differs from previous remote firing variants primarily in the lack of bolt latch allowing for single shots.

The GAU-10/A (NSN or National Stock Number 1005-01-029-3428) has been identified as a member of the Browning M2 family through its inclusion in the June 2000 issue of Countermeasure (Vol 21, No 6, available online here). Countermeasure is published by the Army Ground Risk Management Team, and identifies important issues that soldiers should be aware of with regards to risk management and safety. Beyond this connection, there is no specific information on the GAU-10/A, and it is odd that the only online reference would be from a US Army publication as this is a USAF designation.

XM213/M213, XM218, GAU-15/A, GAU-16/A, and GAU-18/AEdit

The XM213/M213 was a modernization and adaptation of existing .50 caliber AN/M2s in inventory for use as a pintle mounted door gun on helicopters.

The GAU-16/A was an improved GAU-15/A with modified grip and sight assemblies for similar applications.

The GAU-18/A, formerly identified as the XM218, is a lightweight variant of the M2/M3, and is used on the USAF's MH-53J Pave Low II and HH-60 Pave Hawk helicopters. These weapons do not utilize the heavy barrel, and are typically set up as left-hand feed, right-hand charging weapons. In this configuration the gun is fitted with a chute adapter attached to its left hand feed pawl bracket. Thus, the weapon can receive ammunition through a feed chute system connected to internally-mounted ammunition cans. Originally designed to accommodate 1,700 rounds, these cans have since been modified due to space constraints, and now hold about half that amount. However, many aerial gunners find the chute system cumbersome, and opt to install a bracket accommodating the 100-round cans instead (as on the model pictured to the right).

GAU-21/A and M3PEdit

The FN produced M3 series is also in U.S. military service in two versions. One being a fixed remote firing version, the FN M3P, used on the Avenger Air Defense System. The U.S. Army would appear to use this designation for the weapon.

The M3M flexible machine gun has been adopted by the USAF and the USN under the designation GAU-21/A for pintle applications on helicopters.

M2E50 (or M2 E-50)Edit

A long due upgrade program for existing infantry M2s and other M2s currently in U.S. Army service, the E50 finally provides a Quick Change Barrel (QCB) capability, as well as, adding a rail accessory mount, improved flash hider, and a manual safety. While it originally appeared that E50 was within the bounds of the normal U.S. Army designation system, it is actually a developmental project that stands for Enhanced 50 as in enhanced .50 caliber machine gun. The E50 is a conversion kit that can be applied to older weapons — newer machine guns can be produced to this standard, however.

International usageEdit

The M2 family has also been widely used abroad, primarily in its basic infantry configuration. Here is a quick listing of foreign designations for M2 family weapons.

Country NATO Member Designation Description
Australia No M2HB 12.7 x 99 mm Browning M2HB machine gun (manufactured locally under license by Australian Defence Industries[1]
Austria No üsMG M2 12.7 x 99 mm Browning M2HB machine gun
Belgian Army Yes FN M2HB-QCB 12.7 x 99 mm Browning M2HB machine gun, used as infantry weapon, IFV mounted gun and as tank's AA gun
Brazilian Army No Mtr .50 M2 HB "BROWNING" 12.7 x 99 mm Browning M2HB machine gun
Canada Yes M2 12.7 x 99 mm Browning M2HB machine gun
Chilean Army No FN M2HB-QCB 12.7 x 99 mm Browning M2HB machine gun
Denmark Yes M/50 12.7 x 99 mm Browning M2HB machine gun
France Yes Mitrailleuse, 12,7mm, M2 12.7 x 99mm Browning M2HB machine gun
Germany Yes MG50-1 12.7 x 99 mm Browning M2HB machine gun
Israel No מק"כ ("MAKACH") 12.7 x 99 mm Browning M2HB machine gun, used as infantry weapon, IFV mounted gun and as tank's coaxial gun
Japan No 12.7 mm重機関銃M2 (Licensed by Sumitomo Heavy Industries) 12.7 x 99 mm Browning M2HB machine gun, used as IFV mounted gun and as tank's coaxial gun
South Korea No K-6 (Licensed by Daewoo) 12.7 x 99 mm Browning M2HB QCB machine gun
Spain Yes Ametralladora Pesada M-2 HB 12.7 x 99 mm Browning M2HB machine gun
Norway Yes M/50 12.7 x 99 mm Browning M2HB machine gun
Sweden No Tksp 12,7 (Licensed by Bofors) 12.7 x 99 mm Browning M2HB machine gun
United Kingdom (British Army) Yes L2A1 12.7 x 99 mm Browning M2HB machine gun
United Kingdom Yes L6, L6A1 12.7 x 99 mm Browning M2 HB machine gun; ranging gun for the L7 105 mm tank gun on the Centurion tank
United Kingdom Yes L1A1 12.7 x 99 mm Browning M2HB machine gun; ranging gun. called the HMG (heavy machine gun)
United Kingdom Yes L21A1 12.7 x 99 mm Browning M2HB machine gun; ranging gun for the 120 mm tank gun on the Chieftain tank
United Kingdom Yes L111A1 12.7 x 99 mm Browning/FN M2HB QCB machine gun
Switzerland No Mg 64 12.7 x 99 mm Browning M2 HB machine gun

See alsoEdit


External linksEdit