The BL 4-inch Mk IX naval gun[note 1] was a British medium-velocity naval gun introduced in 1917 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.
History
World War I
![](https://upload.wikimedia.org/wikipedia/commons/thumb/7/78/HMS_Repulse_1916-1917_Firth_of_Forth_NH47372_clip.jpg/220px-HMS_Repulse_1916-1917_Firth_of_Forth_NH47372_clip.jpg)
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[4] 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".[5] Guns were thereafter used in single-gun mountings, typically on smaller ships as the main armament.
World War II
![](https://upload.wikimedia.org/wikipedia/commons/thumb/9/96/4_inch_Mk_IX_coast_defence_gun_and_crew_1940_IWM_H_2692.jpg/220px-4_inch_Mk_IX_coast_defence_gun_and_crew_1940_IWM_H_2692.jpg)
![](https://upload.wikimedia.org/wikipedia/commons/thumb/3/32/BL_4_inch_Mk_IX_gun_St_Essylt_1942_AWM_023664.jpeg/220px-BL_4_inch_Mk_IX_gun_St_Essylt_1942_AWM_023664.jpeg)
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.
Surviving examples
- On board HMCS Sackville, the last surviving Flower-class corvette, at Halifax, Nova Scotia, Canada
- A gun at the entrance to the marina in Hull, UK
- A gun at Port Isaac, Cornwall, UK
- Leith Harbour, South Georgia.
See also
Notes
- ^ Mk IX = Mark 9. Britain used Roman numerals to denote Marks (models) of ordnance until after World War II. Mark IX indicates this was the ninth model of BL 4-inch gun.
References
- ^ Campbell, Naval Weapons of WWII, pp.42-43.
- ^ a b Campbell, Naval Weapons of WWII, p.38.
- ^ DiGiulian
- ^ "Jane's Fighting Ships 1919, page 62". Archived from the original on 6 October 2008. Retrieved 18 December 2008.
Bibliography
- Tony DiGiulian, British 4"/45 (10.2 cm) BL Marks IX and X
- Campbell, John (1985). Naval Weapons of World War Two. Naval Institute Press. ISBN 0-87021-459-4.
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