BL 4 inch naval gun Mk VIII

Ordnance BL 4 inch gun Mk VIII
Forward gun of HMS Defender
Type	Naval gun
Service history
In service	1908 - 1945
Used by	United Kingdom Australia
Wars	World War I - World War II
Production history
Designed	1904^[1]
No. built	Mk VIII: 246 Mk XI: 30^[1]
Variants	Mk VIII - Mk XI^[1]
Specifications
Weight	2,912 pounds (1,320 kg) (barrel & breech)^[2]
Barrel length	159.2 inches (4.044 m) bore (40 calibres)^[2]

Shell	31 pounds (14.06 kg) Common pointed, Common lyddite^[2]
Calibre	4 inches (101.6 mm)
Breech	Welin, single-motion screw^[2]
Elevation	-10° to +20°^[1]
Rate of fire	6-8 RPM^[1]
Muzzle velocity	2,287 feet per second (697 m/s)^[3]
Maximum firing range	10,210 yards (9,340 m)^[1]

The BL 4-inch gun Mark VIII^{[note 1]} was a British medium-velocity wire-wound naval gun introduced in 1908 as an anti-torpedo boat gun in smaller ships whose decks could not support the strain of the heavier and more powerful Mk VII gun.^[2]

Mk VIII History

Breech of gun on HMAS Huon in March 1919

The gun succeeded the QF 4 inch Mk III, whose 25-pound (11 kg) shell had been considered insufficiently powerful for its intended role. The BL Mk VIII fired a 31-pound (14 kg) shell. It armed the following warships :

HMS Swift laid down 1905
Tribal-class destroyers from HMS Saracen (1908) onwards.
Beagle-class destroyer of 1909
Acorn-class destroyers of 1910
Acheron-class destroyers of 1910
River-class torpedo-boat destroyers (Australia) of 1910.

The gun was succeeded in its class from 1911 by the QF 4 inch Mk IV.

In World War II many guns were used to arm merchant ships.

Mk XI submarine gun

A Mk XI variant was adapted to arm submarines :

K-class submarines laid down 1915

Notes

↑ Mark VIII = Mark 8. Mark XI = Mark 11. Britain used Roman numerals to denote marks (models) of ordnance until after World War II. This was the eighth model of British BL 4-inch gun.

References

1 2 3 4 5 6 DiGiulian
1 2 3 4 5 HANDBOOK for the 4" Mark VII. and VIII. B.L. Guns 1913
↑ 2287 ft/second firing a 31 lb 3 C.R.H. projectile, using 5 lb 4 oz cordite MD size 16 propellant. HANDBOOK for the 4" Mark VII. and VIII. B.L. Guns 1913.

Sources

HANDBOOK for the 4" Mark VII. and VIII. B.L. Guns 1913 (Corrected to September 1913.) ADMIRALTY Gunnery Branch, G.8652/13

External links

Wikimedia Commons has media related to BL 4 inch Mk VIII naval gun.

Tony DiGiulian, British 4"/40 (10.2 cm) BL Mark VIII and Mark XI

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 US 14 inch 45 cal 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 V 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 pdr 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 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 pdr 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

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