BL 4.7-inch 45-calibre naval gun

The BL 4.7-inch, 45-calibre 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 and Thornycroft type leader. 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 and commissioned in 1926 and 1927

Mk II was a monobloc-barrel 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 They were superseded on new destroyers from 1930 by the QF 4.7-inch Mk IX.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

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