The Browning M2 .50 caliber machine gun is a improved version on the Browning Model 1921 .50 caliber machine gun, which was in turn a development of the Browning M1917 .30 caliber machine gun. The .50 BMG round which the M2 fires is similarly a scaled-up version of the .30-06 round fired by the M1917. The M2 was developed in 1932 as a joint effort by the Army as a heavy barrel ground gun and the Navy as a water cooled anti-aircraft gun. The light weight version developed for aircraft and also used on PT Boats were developed in the late 1930. All three versions were used during World War II by the United States and its Allies. The M2 Heavy Barrel and M2 Aircraft have seen continued service into the 21st century.
Christmas (Jason Statham) is seen using Browning M2 Aircraft heavy machine guns quad-mounted in the nose of the seaplane.