Type Naval gun Number built 2,382 | In service 1916 - 1945 Weight 2 tons barrel & breech | |
 | ||
Used by Royal Navy
Royal Canadian Navy
Free French Navy
Hellenic Navy
Netherlands Navy
New Zealand Navy
Norwegian Navy
South African Navy Wars World War I
World War II | ||
The BL 4-inch gun Mk IX was a British medium-velocity naval gun introduced in 1916 as secondary armament on the Renown-class battlecruisers and Glorious-class "large light cruisers", but which served most notably as the main armament on Flower-class corvettes throughout World War II.
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World War I
The gun was based on the barrel of the QF 4 inch Mk V and the breech mechanism of the BL 4 inch Mk VIII and was first introduced in World War I on capital ships as secondary armament in triple-gun mountings, intended to provide rapid concentrated fire. This turned out to be unworkable in practice. Jane's Fighting Ships of 1919 commented, "4-inch triples are clumsy and not liked. They are not mounted in one sleeve; have separate breech mechanism, a gun crew of 23 to each triple". Guns were thereafter used in single-gun mountings, typically on smaller ships as primary armament.
World War II
In World War II the gun was employed on many small warships such as Flower-class corvettes and minesweepers, primarily for action against surfaced submarines.
This was the last BL 4 inch gun in British service: all subsequent guns have used charges in metal cartridges "QF". It was succeeded on new small warships built in World War II by the QF 4-inch Mk XIX gun which fired a slightly heavier shell at much lower velocity and had a high-angle mounting which added anti-aircraft capability.