The BL 4.7-inch, 45-calibre gun (actually a metric 120 mm gun) was a British medium-velocity naval gun introduced in 1918 for destroyers. It was designed to counter a new generation of heavily armed German destroyers that were believed to be in development.

Description and history

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 : 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 They were superseded on new destroyers from 1930 by the QF 4.7-inch Mk IX.

Ammunition

Weapons of comparable role, performance and era