The .50 Browning Machine Gun round (.50 BMG) was developed at the end of the Great War by John Moses Browning to accompany his new scaled up machine gun. There was a need for a heavier machine gun to act as an anti-aircraft gun and the new cartridge was designed in the dying days of World War One to accompany this new scaled up Browning M1917 MG. The new machine gun did not arrive until 1921 so it would be the Second World War before it came into its own. The British were one of many nations that adopted the Browning .50 cal machine gun as an aircraft gun. British use of the .50 cal as an aircraft gun was limited as although more destructive than .303, by mid war the emphasis was on 20mm cannons which offered far more destruction than the upgrade to .50 offered. Today we are looking at a US manufactured, World War Two dated .50BMG round:
The round has a heavy 13mm diameter projectile which with a 290 grain loading has a velocity of around 900 m/s:
The round is rimless and has a deem extractor groove cut into the base of the cartridge:
This particular round is marked DM and has a date of 1943:
DM stands for Des Moines Ordnance Plant – Ankeny, Iowa.
Before the war a number of weapons were evaluated for aircraft use, including .303″ machine guns (Vickers and Colt-Browning), .50″ weapons, and 20mm cannon. This involved both comparison of their statistics, and firing trials for performance, reliability, and effectiveness against aircraft targets.
The conclusion reached was that – for a given weight of armament, and allowing for fifteen seconds or so of firing time – eight .303″ Colt-Brownings could be carried by a single-engined monoplane, and would deliver some 160 rounds a second.
The .50″ Browning could, in the same weight, manage three guns, achieving 30–40 rounds a second; and while the larger weapon was more destructive, individual hits were not four times deadlier, while the larger number of .303″ bullets increased the chance of doing lethal damage.
The most effective weapon evaluated, the 20mm Hispano cannon, had a good muzzle velocity, high rate of fire, and used explosive shells with much greater effect on the target; but the desired armament of four cannon (to get enough rounds on target in a short exposure) was a much heavier installation, and the early Hispano was drum-fed and needed a very rigid mounting: it worked well in aircraft like the Westland Whirlwind, but needed development to go in a monoplane’s wings (the first effort to arm Spitfires with cannon failed badly).
So, the default fighter armament was 8 x .303″ guns, with intent to switch to 4 x 20mm cannon once aircraft could carry that weight. This pre-war approach shifted slightly with the Spitfire swapping four .303″ for two cannon; later in the war, the Spitfire’s ‘E’ wing carried two 20mm cannon and two .50″ Brownings, before the last versions went to four 20mm. Other fighters, like the Hawker Typhoon and Fairey Firefly, went directly to quadruple cannon and stayed there; there wasn’t an intermediate step of using .50″ weapons.
Combat experience generally suggested that the .50″ and similar weapons fell into an awkward niche: lacking explosive rounds, and with limited armour-piercing capability, they were quickly limited in utility against aircraft or tanks, with 20mm weapons largely replacing them. Meanwhile, they and their ammunition were heavy, meaning they really needed vehicles to carry and move them.