The M2 Machine Gun, or Browning .50 Caliber Machine Gun is a heavy machine gun designed towards the end of World War I by John Browning. It was nicknamed Ma Deuce by US troops or simply called "fifty-cal." in reference to its caliber. The design has had many specific designations; the official designation for the current infantry type is Browning Machine Gun, Cal. .50, M2, HB, Flexible. It is effective against infantry, unarmored or lightly-armored vehicles and boats, light fortifications, and low-flying aircraft.
The Browning .50 caliber machine gun has been used extensively as a vehicle weapon and for aircraft armament by the United States from the 1920s 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 as well. It is still in use today, with only a few modern improvements. The M2 has been in use longer than any other small arm in U.S. inventory. It was very similar in design to the smaller Browning Model 1919 machine gun.
A variant without a water jacket, but with a thicker-walled, air-cooled barrel superseded it (air-cooled barrels had already been used on variants for use on aircraft, but these quickly overheated in ground use). This new variant was then designated the M2 HB (HB for Heavy Barrel). The added mass and surface area of the new barrel compensated, somewhat, for the loss of water-cooling, while reducing bulk and weight (the M2 weighed 121 lb (55 kg), with water, whereas the M2 HB weighs 84 lb). 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 is a scaled-up version of John Browning's M1917 .30 caliber machine gun (even using the same timing gauges), fires the .50 BMG cartridge, which today is also used in high-powered sniper rifles and long range target rifles due to its excellent long range accuracy, external ballistics performance, incredible stopping power, and lethality. The M2 is an air-cooled, belt-fed, machine gun that fires from a closed bolt, 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.
The M2 has varying cyclic rates of fire, depending upon the model. The M2HB (heavy barrel) air-cooled ground gun has a cyclic rate of 450-575 rounds per minute. The early M2 water-cooled AA guns had a cyclic rate of around 450-600 rpm. The AN/M2 aircraft gun has a cyclic rate of 750-850 rpm; this increases to 1,200 rpm or more for AN/M3 aircraft guns fitted with electric or mechanical feed boost mechanisms. These maximum rates of fire are generally not achieved in use, as sustained fire at that rate will wear out the bore within a few thousand rounds, necessitating replacement. The M2HB's sustained rate of fire is considered to be anything less than 40 rounds per minute.
The M2 has a maximum range of 7.4 kilometers (4.55 miles), 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). In this configuration, the V-shaped "butterfly" trigger is located at the very rear of the weapon, with a "spade handle" hand-grip on either side of it and the bolt release the center. The spade handles are gripped and the butterfly trigger is depressed with one or both thumbs. Recently new rear buffer assemblies have used squeeze triggers mounted to the hand grips, doing away with the butterfly triggers.
When the bolt release is locked down by the bolt latch release lock on the buffer tube sleeve, the gun functions in fully automatic mode. Conversely, the bolt release can be unlocked into the up position resulting in single-shot firing (the gunner must press the bolt latch release to send the bolt forward). Unlike virtually all other modern machine guns, it has no safety (although a sliding safety switch has recently been fielded to USMC armorers for installation on their weapons).
Because the M2 was intentionally designed to be fit into many configurations, it can be adapted to feed from the left or right side of the weapon by exchanging the belt-holding pawls, the belt feed pawl, and the front and rear cartridge stops, then reversing the bolt switch. The conversion can be completed in under a minute with no tools.
There are several different types of ammunition used in the M2HB. From World War II through the Vietnam War, the M2 was issued with standard ball, armor-piercing (AP), armor-piercing incendiary (API), and armor-piercing incendiary tracer (APIT) rounds. All .50 ammunition designated "armor-piercing" was required to completely perforate 0.875" (22.2 mm) of hardened steel armor plate at a distance of 100 yards (91 m), and 0.75" (19 mm) at 547 yards (500 m). The API and APIT rounds left a flash, report, and smoke on contact, useful in detecting strikes on enemy targets; they were primarily intended to incapacitate thin-skinned and lightly armored vehicles and aircraft, while igniting their fuel tanks.
Current ammunition types include: M33 Ball (706.7 grain) for personnel and light material targets, M17 tracer, M8 API (622.5 grain), M20 API-T (619 grain), and M962 SLAP-T. The latter ammunition along with the M903 SLAP (Saboted Light Armor Penetrator) round can perforate 1.34 in (34 mm) of HHA (high hard armor, or face-hardened steel plate) at 500 meters, 0.91 in (23 mm) at 1,200 meters, and 0.75 in (19 mm) at 1,500 meters. This is achieved by using a .30 inch diameter tungsten penetrator. The SLAP-T adds a tracer charge to the base of the ammunition. This ammunition was type classified in 1993.
When firing blanks, a large blank-firing adapter (BFA) must be used to keep the gas pressure high enough to allow the action to cycle. The adapter is very distinctive, attaching to the muzzle with three rods extending back to the base. The BFA can often be seen on M2s during peacetime operations.
An M2 fired from a rigid-hulled inflatable boat.
A U.S. Marine mans a .50 caliber machine gun as part of a security force during an exercise
The M2 .50 Browning machine gun has been used for various roles:
* A medium infantry support weapon
* As an anti-aircraft (AA) gun in some ships; up to six M2 guns could be mounted on the same turret.
* As an anti-aircraft gun on the ground. The original water-cooled version of the M2 was used on a tall AA tripod or vehicle-mounted anti-aircraft weapon on a sturdy pedestal mount. In later variants, twin and quadruple M2HB Brownings were used, such as the quad .50 AA mount used on the US M16 half-track carrier. Twin or quad-mount .50 M2 guns normally used alternating left-hand and right-hand feed.
* Primary or secondary weapon on an armored fighting vehicle.
* Primary or secondary weapon on a naval patrol boat.
* Secondary weapon for anti-boat defense on large naval vessels (corvettes, frigates, destroyers, cruisers, etc).
* Coaxial gun or independent mounting in some tanks.
* Fixed-mounted primary armament in World War II-era U.S. aircraft such as the P-47 Thunderbolt, P-51 Mustang, and the Korean-era U.S. F-86 Sabre.
* Fixed or flexible-mounted defensive armament in World War II-era bombers such as the B-17 Flying Fortress, and B-24 Liberator.
At the outbreak of the Second World War the United States had versions of the M2 in service as fixed aircraft guns, anti-aircraft defensive guns (on aircraft, ships, or boats), infantry (tripod-mounted) guns, and as dual purpose anti-aircraft and anti-vehicular weapons on vehicles.
The .50 AN/M2 light-barrel aircraft Browning was used in planes, had a rate of fire of approximately 800 rounds per minute, and was used singly or in groups of up to eight guns for aircraft ranging from the P-47 Thunderbolt to the B-25 Mitchell bomber.
In the dual-purpose vehicle mount, the M2HB (heavy barrel) proved extremely effective in U.S. service: the Browning's .50 caliber AP and API rounds could easily penetrate the engine block or fuel tanks of a German ME-109 fighter attacking at low altitude, or perforate the hull plates and fuel tanks of a German half-track or light armored car. While the dual-purpose mounting was undeniably useful, it did normally require the operator to stand when using the M2 in a ground role, exposing him to return fire. Units in the field often modified the mountings on their vehicles, especially tanks and tank destroyers, to provide more operator protection in the anti-vehicular and anti-personnel role. The weapon was particularly hated by the Germans, whose attacks against otherwise helpless stalled motor convoys were frequently broken up by .50 caliber machine gun fire.
Mounted on a heavily-sandbagged tripod, the M2HB proved very useful in either a defensive role or to interdict or block road intersections from use by German infantry and motorized forces. The hammering of a heavy Browning could usually be relied upon to put a German infantry company face-down in the dirt. There are numerous instances of the M2 Browning being used against enemy personnel, particularly infantry assaults or for interdiction or elimination of enemy artillery observers or snipers at distances too great for ordinary infantry weapons.
A quadruple mount of four .50 M2HB guns with a single gunner situated behind an armored pod was used by U.S. AA battalions in either a towed trailer or mounted in a half-track carrier (M16 AA half-track). With 200 rounds per gun in a powered tracking mount, the guns proved very effective against low-flying aircraft. Towards the end of the war, as Luftwaffe attacks grew more infrequent, the quad .50 (nicknamed the Meat Chopper) was increasingly used in an anti-personnel role. Snipers firing from trees were engaged by the quad gunner at trunk level - the weapon would cut down and destroy the entire tree, and the sniper with it.
M16 .50 AA Quad aka the 'Meat Chopper'
The M2HB was not widely used in the Pacific campaign, due to several factors, including weight, the inherent nature of infantry jungle combat, and because road intersections were usually easily outflanked. However, it was used by fast-moving motorized forces in the Phillippines to destroy Japanese blocking units on the advance to Manila. The quad mount .50 was also used to destroy Japanese emplacements.
The M2HB saw service in both Korea and Vietnam. In 2003, during the Iraq War, U.S. Army Sgt. Paul R. Smith used his M2HB to kill twenty to fifty Republican Guard troops attacking a U.S. Army outpost, allowing wounded soldiers to be evacuated and saving an aid station from being overrun.
Commonwealth use of the M2 Browning .50 caliber machine gun (known as the .5 Browning in British and Commonwealth service) was limited in the Second World War, though from 1942 it was standard armament on US-built/designed AFVs such as the M4 Sherman, M8 Greyhound, or M10 Wolverine that began to see use in British, Canadian, Australian and New Zealand units. Nevertheless, the heavy Browning's effectiveness was praised by many British and Commonwealth soldiers in infantry, armored, and ordnance branches. Many commanders thought the .5 Browning the best weapon in its class, certainly the best of the American weapons, including the M1 Garand and carbine. In North Africa, after Commonwealth units began to obtain sufficient parts, manuals, gauges, and ammunition for the new weapon, the .5 Browning was increasingly used, eventually replacing the 15mm Besa, but in Italy was often deleted from top turret mountings because the mount exposed the operator to low branches and enemy fire. Some SAS units used the aircraft (AN/M2) version of the gun, while turret-mounted .5 Brownings were used later in the war in such aircraft as the Lancaster bomber.
After the Second World War, the .5 Browning continued to see action in Korea and other theaters, in aircraft, tripod (ground), and vehicle mounts. One of its most notable actions in a ground role was in a fierce battle with a nine-man SAS team at the Battle of Mirbat in Oman in July 1972, where the heavy Browning and its API ammunition was used to help repulse an assault by 250 Yemeni Adoo guerrillas.
M2 as 'Sniper rifle'
The M2 machine gun has been used in a single instance as a long-range sniper rifle, when equipped with a telescopic sight. This use was discovered by US Marine sniper Carlos Hathcock during the Vietnam War. Using a Unertl telescopic sight and a mounting bracket of his own design, Hathcock could quickly convert the M2 into a rifle, using the traversing-and-elevating (T & E) mechanism attached to the tripod to assist in aiming at stationary targets. When firing semi-automatically (possible because of the M2's low cyclic rate), Hathcock could accurately hit man-size targets at up to 2000 yards — twice the range of a rifle-caliber sniper rifle.
Variants and derivatives
An M2HB in the French Foreign Legion's 2nd Infantry Regiment during an exercise
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 development of the M1921 water-cooled machine gun which led to the M2, meant that the initial M2s were in fact water-cooled. These weapons were designated Browning Machine Gun, Cal. .50, M2, Water-Cooled, Flexible. There was no fixed water-cooled version.
Improved 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.
A number of additional subvariants were developed after the end of the Second World War. The Caliber .50 Machine Gun, Browning, M2, Heavy Barrel, M48 Turret Type was developed for the commander's cupola on the M48 Patton tank. The cupola mount on the M48-A3 was thoroughly disliked by most tankers, as it proved unreliable in service. A cupola-mounted M2 was later adopted for the commander's position on the M1 Abrams tanks. Three subvariants were also developed for used by the US Navy on a variety of ships and watercraft. These included the Caliber .50 Machine Gun, Browning, M2, Heavy Barrel, Soft Mount (Navy) and the Caliber .50 Machine Gun, Browning, M2, Heavy Barrel, Fixed Type (Navy). The fixed types fire from a solenoid trigger and come in left or right hand feed variants for use on the Mk 56 Mod 0 dual mount and other mounts.
M2 E-50 (M2E50)
A long overdue upgrade program for existing infantry M2HBs and other M2s currently in U.S. Army service, the E50 provides a: Quick Change Barrel (QCB) capability, a rail accessory mount, an improved flash hider and a manual safety.
The E50 designation initially appeared to be within the bounds of the normal U.S. Army designation system. However, it later turned out that the term was in fact a developmental project that stands for Enhanced 50, as in enhanced .50 caliber machine gun. Developed primarily as a conversion kit for existing weapons, it is likely that new production machine guns will be built to this standard. In later U.S. Army briefings, this variant has been referenced as the M2E2 or M2A1.
AN/M2 and AN/M3
The M2 machine gun was widely used during World War II and in later postwar conflicts as a remote or flexible aircraft gun. For fixed (offensive) or flexible (defensive) guns used in aircraft, a dedicated M2 version was developed called the .50 Browning AN/M2. The AN/M2 had a cyclic rate of 750-850 rounds per minute, with the ability to be fired from a electrically-operated remote-mount solenoid trigger when installed as a fixed gun. Cooled by the aircraft's slip-stream, the air-cooled AN/M2 was fitted with a substantially lighter barrel, which also had the effect of increasing the rate of fire. The official designation for this weapon was Browning Machine Gun, Aircraft, Cal. .50, AN/M2 (Fixed) or (Flexible). During World War II, a faster-firing .50-inch aircraft Browning was developed, the AN/M3, using a mechanical or electrically-boosted feed mechanism to increase the rate of fire to around 1,200 rounds per minute. The AN/M3 was widely used in Korea on such planes as the the F-86 Sabre and in Vietnam in the XM14/SUU-12/A gun pod.
The XM296/M296 is a further development of the AN/M2 and AN/M3 machine gun for remote firing applications, and is currently only used in an armament system for 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. ). 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/A
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 using the M59 armament subsystem.
The GAU-15/A, formerly identified as the XM218, is a lightweight member of the M2/M3 family. The GAU-16/A was an improved GAU-15/A with modified grip and sight assemblies for similar applications. Both of these weapons were used as a part of the A/A49E-11 armament subsystem (Also known as the Defensive Armament System).
The GAU-18/A, is a lightweight variant of the M2/M3, and is used on the USAF's MH-53 Pave Low 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.
GAU-21/A and M3P
The FN produced M3 series is also in U.S. military service in two versions. The fixed remote firing version, the FN M3P, is used by the U.S. Army on the Avenger Air Defense System. 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.