Lewis gun  The Lewis gun (or Lewis automatic machine gun or Lewis automatic rifle) is a First World War–era light machine gun. Designed privately in America but not adopted, the design was finalised and mass-produced in the United Kingdom, and widely used by troops of the British Empire during the war. It had a distinctive barrel cooling shroud (containing a finned, aluminium breech-to-muzzle heat sink to cool the gun barrel) and top-mounted pan magazine. The Lewis served to the end of the Korean War. It was also widely used as an aircraft machine gun, almost always with the cooling shroud removed (as air flow during flight offers sufficient cooling), during both World Wars. The Lewis gun was invented by U.S. Army colonel Isaac Newton Lewis in 1911, based on initial work by Samuel Maclean. Despite its origins, the Lewis gun was not initially adopted by the U.S. military, most likely because of political differences between Lewis and General William Crozier, the chief of the Ordnance Department. Lewis became frustrated with trying to persuade the U.S. Army to adopt his design, "slapped by rejections from ignorant hacks", in his words, and retired from the army. He left the United States in 1913 and went to Belgium, where he established the Armes Automatique Lewis company in Liège to facilitate commercial production of the gun. Lewis had been working closely with British arms manufacturer the Birmingham Small Arms Company Limited (BSA) in an effort to overcome some of the production difficulties of the weapon. The Belgians bought a small number of Lewises in 1913, using the .303 British round and, in 1914, BSA purchased a licence to manufacture the Lewis machine gun in England, which resulted in Lewis receiving significant royalty payments and becoming very wealthy. Lewis and his factory moved to England before 1914, away from possible seizure in the event of a German invasion. The onset of the First World War increased demand for the Lewis gun, and BSA began production, under the designation "Model 1914". The design was officially approved for service on 15 October 1915 under the designation "Gun, Lewis, .303-cal." No Lewis guns were produced in Belgium during the war; all manufacture was carried out by BSA in England and the Savage Arms Company in the US. The Lewis was produced by BSA and Savage Arms during the war, and although the two versions were largely similar, enough differences existed to stop them being completely interchangeable, although this was rectified by the time of the Second World War.