BL 4-inch Mk IX naval gun

Ordnance BL 4-inch Mk IX gun
Ordnance BL 4-inch Mk IX gun
	On Flower-class corvette HMCS Calgary in World War II
Type	Naval gun
Service history
In service	1917–1945
Used by	Royal Navy; Royal Canadian Navy; Free French Navy; Hellenic Navy; Royal Indian Navy; Netherlands Navy; Royal New Zealand Navy; Norwegian Navy; South African Navy
Wars	World War I; World War II
Production history
No. built	2,382
Specifications
Mass	2 tons barrel & breech
Barrel length	180 inches (4.572 m) bore (45 calibres)
Shell	31 pounds (14.1 kg)
Calibre	4 inches (101.6 mm)
Breech	Welin interrupted screw
Elevation	-10 degrees to +30 degrees
Rate of fire	10-12 rpm
Muzzle velocity	800 metres per second (2,600 ft/s)
Maximum firing range	12,660 metres (13,850 yd)

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

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

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, USA

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 ^c http://navalhistory.flixco.info/H/77826x53535/8330/a0.htm^{[dead link]}
^ ^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.

External links

[4] 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.

[1] Campbell, Naval Weapons of WWII, pp.42-43.

[navalhistory.flixco.info-2] ttp://navalhistory.flixco.info/H/77826x53535/8330/a0.htm^{[dead link]}

[Campbell,_p.38-3] Campbell, Naval Weapons of WWII, p.38.

[5] DiGiulian

[6] "Jane's Fighting Ships 1919, page 62". Archived from the original on 6 October 2008. Retrieved 18 December 2008.

[1]

[2]

[3]

[note 1]

[4]

[5]

v t e British Empire naval weapons of the First World War
Monitor guns	BL 9.2-inch Mk VI BL 9.2-inch Mk VIII BL 9.2-inch Mk X BL 9.2-inch Mk XII BL 12-inch Mk VIII BL 14-inch Mk II (US built) BL 15-inch Mk I BL 18-inch Mk I
Capital ship main armament	Vickers 10-inch 45 cal. EOC 10-inch 45 cal. BL 12-inch Mk VIII BL 12-inch Mk IX BL 12-inch Mk X BL 12-inch Mk XI & XII EOC 12-inch 45 cal. Mk XIII BL 13.5-inch Mk I – IV BL 13.5-inch Mk V BL 13.5-inch Mk VI EOC 14-inch 45 cal. Mk I BL 15-inch Mk I
Armoured cruiser main armament	BL 7.5-inch Mk I BL 9.2-inch Mk X BL 9.2-inch Mk XI
Secondary armament and light cruiser main armament	QF 12-pounder 18 cwt QF 14-pounder Maxim-Nordenfelt QF 14-pounder Mk I & II QF 4-inch Mk III BL 4-inch Mk VII QF 4-inch Mk V BL 4-inch Mk IX BL 5.5-inch Mk I QF 6-inch Mk I – III BL 6-inch Mk VII BL 6-inch Mk XI BL 6-inch Mk XII BL 6-inch Mk XIII-XVIII BL 7.5-inch Mk II – Mk V
Destroyer and small cruiser armament	QF 12-pounder 12 cwt Mk II QF 4-inch Mk III BL 4-inch Mk VIII QF 4-inch Mk IV BL 4.7-inch Mk I
Merchant ship armament	QF 4.7-inch Mk I – IV QF 4.7-inch Mk V*
Submarine guns	BL 4-inch Mk XI QF 4-inch Mk XII
Anti-aircraft guns	QF 2-pounder "pom-pom" Mk II QF 3-inch 20 cwt QF 4-inch Mk V
Light weapons	.303 Vickers machine gun QF 3-pounder Hotchkiss QF 3-pounder Vickers QF 6-pounder Hotchkiss
Torpedoes	18-inch Mk V – VIII 21-inch Mk II 21-inch Mk IV
Mines	Spherical Mk I, II and III Vickers Elia mine Type H mine
Anti-submarine weapons	Type A Depth charge Type B Depth charge Type C Depth charge Type D Depth charge Type E Depth charge Type F Depth charge Type G Depth charge Cruiser Mine 7.5-inch howitzer
Landing guns	QF 12-pounder 8 cwt

v t e British Commonwealth naval weapons of the Second World War
Monitor guns	BL 15-inch
Capital ship main armament	BL 14-inch BL 15-inch BL 16-inch
Heavy cruiser main armament	BL 7.5-inch Mk VI BL 8-inch Mk VIII
Secondary armament and light cruiser main armament	QF 4-inch Mk V QF 4.5-inch QF 5.25-inch BL 5.5-inch BL 6-inch Mk XII BL 6-inch Mk XXII BL 6-inch Mk XXIII
Minesweeper, Sloop, Corvette, Frigate and Destroyer armament	QF 6-pounder 10 cwt QF 12-pounder 12 cwt Mk V QF 4-inch Mk IV BL 4-inch Mk IX QF 4-inch Mk XVI QF 4-inch Mk XIX QF 4.5-inch BL 4.7-inch Mk II QF 4.7-inch Mk IX & XII QF 4.7-inch Mk XI
Submarine guns	QF 12-pounder 12 cwt Mk V QF 3-inch 20 cwt QF 4-inch Mk XII & XXII
Anti-aircraft weapons	Unrotated projectile Holman Projector 20 mm Oerlikon QF 2-pounder "pom-pom" Mk VIII 40 mm Bofors QF 3-inch 20 cwt QF 4-inch Mk V QF 4-inch Mk XVI QF 4.5-inch QF 4.7-inch Mk VIII
Light weapons	.303 Lewis machine gun .50 Vickers Mk III machine gun QF 3-pounder Vickers
Torpedoes	21-inch Mk VII 21-inch Mk VIII 21-inch Mk X 21-inch Mk XI 24.5-inch Mk I
Anti-submarine weapons	Thornycroft depth charge thrower Hedgehog Squid
Small craft armament	Molins 6-pounder Vickers K machine gun 18-inch torpedo
Foreign-sourced weapons	20 mm Oerlikon 40 mm Bofors 3-inch 23 caliber gun (US) 3-inch 50 caliber gun (US) 4-inch 50 caliber Mark 9 gun (US) 5-inch 51 caliber Mark 8 gun (US) Y-gun depth charge projector (US) Mark 8 torpedo (US)