The Scarff ring was a type of machine gun mounting developed during the First World War by Warrant Officer (Gunner) F. W. Scarff of the Admiralty Air Department for use on two-seater aircraft. The mount incorporated bungee cord suspension in elevation to compensate for the weight of the gun, and allowed an airgunner in an open cockpit to swivel and elevate his weapon (a Lewis machine gun) quickly, and easily fire in any direction. Later models permitted the fitting of two Lewis guns; while this doubled the firepower available, operation of the paired guns was more cumbersome, and required considerable strength from the gunner, especially at altitude, so that many gunners preferred the original single gun - and this became the postwar standard. In either case, the mounting was simple, rugged, and gave its operator an excellent field of fire. It was widely adapted and copied for other airforces.
As well as becoming a standard fitting in the British forces during the First World War, the Scarff ring was used in the postwar Royal Air Force for many years. Perhaps the last British aircraft to use the mounting was the Supermarine Walrus amphibian prototype.
Scarff was also involved in the development of the Scarff-Dibovsky interrupter gear.
Although it was a seemingly simple device, later attempts to emulate the Scarff ring as a mounting for the dorsal Vickers K in the World War II Handley Page Hampden bomber were failures. Handley Page had designed a carriage with ball-bearing wheels running on a track around the cockpit. Vibration when firing shook the balls out, jamming the mounting.
In British use the Scarff ring was replaced in the 1930s by specialised power-operated turrets such as those made by Boulton Paul or Nash & Thompson, aircraft airspeeds having by then risen to the point where a manually-operated gun was infeasible.