BL 13.5-inch Mk V naval gun
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The BL 13.5 inch Mk V gun was a British heavy naval gun, introduced in 1912 as the main armament for the new super-dreadnought battleships of the Orion class. The calibre was 13.5 inches and the barrels were 45 calibres long i.e. 607.5 inches. Wikipedia
Barrel length: Bore 50 ft 6 in (15.392 m) (45 cal)
Calibre: 13.5-inch (342.9 mm)
Muzzle velocity: H: 2,491 ft/s (759 m/s); L: 2,582 ft/s (787 m/s)
Shell: H: 1,400 lb (635.03 kg); L: 1,250 lb (566.99 kg) HE, AP
Used by: United Kingdom