Volley gun
The Ribauldequin was a medieval version of the volley gun. It had its barrels set up in parallel. This early version was first employed during the Hundred Years' War by the army of Edward III of England, in 1339. Later on, the late Swiss army employed it.
11×59mmR Gras
By 1917 it had been determined that standard rifle calibre cartridges were less satisfactory for balloon busting (shooting down observation balloons) than larger calibres carrying incendiary or tracer bullets. The French adapted the standard 11x59mmR Gras cartridge to fire from their Hotchkiss M1914 machine gun as an aircraft gun. Later the more reliable and more easily synchronised Vickers machine gun was chambered in the round, known as the "Vickers aircraft machine gun" and sometimes the "balloon buster", it fired the same cartridge with incendiary bullets and disintegrating belt link, the cartridge became known as the "11mm Vickers" in British service. The Vickers aircraft machine gun and the 11mm Vickers was adopted by the allies as a standard anti-balloon armament and used by both the British and French in this role until the end of the war, as well as other allies such as Belgium and the United States of America. Notable users include Belgium's leading fighter ace and the allies' champion balloon buster Willy Coppens, and America's two highest scoring fighter aces, Eddie Rickenbacker and Frank Luke.