The M2 Machine Gun, or Browning .50 Caliber Machine Gun is a heavy machine gun designed just after World War I by John Browning. It is nicknamed Ma Deuce by US troops or simply called fifty caliber machine gun. The design has had many specific designations- the official designation for the infantry type is Browning Machine Gun, Heavy Barrel, Cal. .50, M2, HB, Flexible. The Browning .50 machine gun was 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, Korean War, the Vietnam Conflict, as well as during operations in Iraq in the 1990s and 2000s. Its is the primary heavy machine gun of NATO countries, and has been used many other countries. It is still in use today

The M2 fires the .50 BMG cartridge that was designed for this weapon, 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, all at a cyclic rate of 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 has a maximum range of almost 7 kilometers (4.2 miles), but its maximum effective range is roughly 2 kilometers (1.2 miles) when fired from a stable mount, such as a tripod or vehicle. 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 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 in the center. The "spade handles" 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.