BL 4.7 inch/45 gun

• Name — BL 4.7-inch (120 mm), 45-calibre naval gun • Type — Naval gun • Is Ranged — yes • Is Artillery — yes • Is Uk — yes • Service — 1919–1948 • Used By — United Kingdom • Wars — World War II • Design Date — Mk I: 1918 Mk II: 1940 • Production Date — Mk I: 1919 Mk II: 1940 • Number — Mk I: 187 Mk II: 32 • Variants — Mk I, Mk II • Weight — Mk I: 7000 lb Mk II: 7028 lb • Part Length — 5.4 m bore (45 calibres) • Cartridge — 50 lb • Caliber — 4.724 in • Rate — 5-6 RPM • Velocity — 814 m/s • Max Range — 14450 m at 30° • Breech — Welin breech block • Elevation — -9.5° to +30° • Traverse — -120° to +120°

• Illustration — Gunners on destroyer Broke, September 1940 • Illustration — On a Landing Craft Gun (L), preparing for the Invasion of Normandy, 1944 Mk I, of built-up wire-wound construction with a propellant charge in a cloth bag, went into service beginning in 1918 on destroyers of the new Admiralty type destroyer leader (Scott class) and Thornycroft type leader (Shakespeare class). Some saw service in World War I, but most entered service after the war ended. It was also mounted on: • s as re-gunned in 1918 • Thornycroft and Admiralty Modified W-class destroyers completed 1919–1920 • Prototype destroyers Ambuscade and Amazon commissioned in 1926 and 1927 Mk II was a monobloc-barrel (i.e. single-piece, typical of small to medium World War II guns) gun of similar performance introduced in World War II to replace the worn-out Mk I guns on surviving ships. These were the only BL-type 4.7-inch guns in British service; all others have been of the QF-type. They were superseded on new destroyers from 1930 by the QF 4.7-inch Mk IX.

• Illustration — Mk IIA S.A.P. (semi-armour piercing) shell, 1933

• Type 3 120 mm 45 caliber naval gun: Japanese equivalent • 5"/51 caliber gun: US Navy equivalent