Browning guns held a certain level of excellence in their design that they were ultimately manufactured beyond United States soil due to their global popularity. The British Royal Air Force (RAF) adopted a version of the belt-fed M1919 which was itself an air-cooled evolution of the original World War 1-era, water-cooled M1917. The British variant was designated Browning .303 as it was chambered to fire the British .303 / 7.7mm rifle cartridge. It went on to be used aboard a plethora of warplanes concerning the British cause of World War 2.
The Browning .303 was selected as a replacement for the Vickers .303 and produced locally by Birmingham Small Arms (BSA) Company.
The British form was based largely on the earlier Colt-Browning 1930 Pattern machine gun and introduced an open-bolt change to the internals. In its base aircraft fighting form, it would be arranged to fire from a hydraulic configuration within the wing of an aircraft but other variants were soon pushed through as battlefield need dictated including a trainable, hand-fired (with manual cocking handle) in-aircraft types as well as turret-mounted types. In the end, the weapon was so important to the British war effort that it came to be known as the weapon that "won the Battle of Britain". Both the storied Supermarine Spitfire and Hawker Hurricane fighters carried this distinguished weapon as wing-mounted armament and the Avro Lancaster bomber - a legend in its own right - feature the gun in its turret emplacements (a quad-arrangement was seated at the tail).
The selection of the American design spawned from a 1934 search by the RAF for a reliable belt-fed, air-cooled vehicle weapon to feature aboard its aircraft. The choice whittled down to the Colt-Browning offering and an entry put forth by Vickers - the "Vickers Central Action" (VCA) with the Colt-Browning effort winning out. After securing local production rights with the American company, the weapon's local manufacture was charged to BSA and Vickers in 1935. However, only BSA contributed to the total production figures as Vickers was already committed to other machine gun efforts by then.
Initial forms were delivered from Colt during 1936-1937 and were designated locally as "Mark I". This model was designed to accept the ammunition belt from either side of the weapon which made it easily adaptable to the wings of British warplanes without much modification on the gun itself. Upgrades to the series brought along the Mark I* and Mark I** designations as auxiliary sear units were added to the design in an effort to prevent readied ammunition from freely "cooking off" in the hot weapon after a period of sustained fire. In 1937 there arrived the "Mark II" which installed a BSA-developed sear system which further improved the weapons performance in combat - indeed the Mark II is noted as the definitive variant of the British Browning .303 series as a whole. The Mark II* used a fluted muzzle collar and had a finned flash suppressor.
Around 468,000 Browning .303 machine guns were built before the end of World War 2 which arrived in August of 1945 - providing itself a spectacularly reliable and functional weapon worthy of wartime use.