motor boats and "armed yachts". It was used almost exclusively in the single-barrel, unpowered pedestal mountings P Mark II (Royal Navy nomenclature gave mountings and guns separate Mark numbers) except for a small number of weapons on the mounting Mark XV, which was a twin-barreled, powered mount. These were too heavy to be of any use at sea and were mounted ashore. All were scrapped by 1944. Calibre: 40 mm L/39 Total length: . Length of bore: . Rifling: Polygroove, plain section, , uniform twist 1 in , 12 grooves. Weight of gun & breech assembly: Shell Weight: HE. Rate of Fire: 200 rpm Effective Range: Muzzle Velocity: Some 7,000 guns were made. The gun was also used by the Japanese as the 40 mm/62 "HI" Shiki. The Regia Marina also used it from the Great War throughout World War II. It was superseded in the 1930s as a primary AA weapon on Italian warships by more modern guns, such as the Cannone-Mitragliera da 37/54 (Breda). QF 2-pounder Mark VIII The Royal Navy had identified the need for a rapid-firing, multi-barrelled close-range anti-aircraft weapon at an early stage. Design work for such a weapon began in 1923 based on the earlier Mark II, undoubtedly to use the enormous stocks of 2-pounder ammunition left over from the First World War. Lack of funding led to a convoluted and drawn-out design and trials history and it was not until 1930 that these weapons began to enter service. Known as the QF 2-pounder Mark VIII, it is usually referred to as the "multiple pom-pom". The initial mounting was the 11.8 to 17.35 ton, eight-barrelled mounting Mark V (later Mark VI), suitable for ships of cruiser and aircraft carrier size upward. From 1935, the quadruple mounting Mark VII, essentially half a Mark V or VI, entered service for ships of destroyer and cruiser size. These multiple gun mounts required four guns and were nicknamed the "Chicago Piano". The mount had two rows each of two or four guns. Guns were produced in both right- and left-hand and "inner" and "outer" so that the feed and ejector mechanisms matched. Single-barrelled mounts, the Mark VIII (manual) and Mark XVI (power operated), were also widely used, mainly in small escorts (such as the Flower-class corvettes) and coastal craft (especially early Fairmile D motor torpedo boats). The Mark XVI mounting was related to the twin mounting Mark V