BL 4-inch Mk VII naval gun explained

Ordnance BL 4-inch gun Mk VII
Origin:	United Kingdom
Type:	Naval gun
Is Ranged:	yes
Is Artillery:	yes
Is Uk:	yes
Service:	1908–1945
Used By:	United Kingdom
Wars:	World War I World War II
Number:	600^[1]
Weight:	4704lb (barrel & breech)
Part Length:	201.25inches bore (50.3 calibres)^[2]
Cartridge:	31lb Common pointed, Common lyddite
Caliber:	4inches
Rate:	6-8 rpm
Velocity:	2852ft/s^[3]
Max Range:	11600yd at 15°^[4]
Breech:	Welin, Single-motion screw
Elevation:	-10 degrees to +15 degrees^[5]

The BL 4-inch gun Mk VII^[6] was a British high-velocity naval gun introduced in 1908 as an anti-torpedo boat gun in large ships, and in the main armament of smaller ships. Of the 600 produced, 482 were still available in 1939^[7] for use as coastal artillery and as a defensive weapon on Defensively Equipped Merchant Ships (DEMS) during the Second World War.

Naval history

The guns armed the following warships :

• s, laid down 1906
• s, laid down 1907
• scout cruisers, laid down 1907
• , laid down 1909
• battleships, laid down 1909
• s, laid down 1909
• s, laid down 1909
• s, laid down 1909
• Bristol-class light cruisers, laid down 1909
• scout cruisers, laid down 1909
• scout cruisers, laid down 1910
• battleships, laid down 1911

The gun was succeeded in the "heavy" 4-inch class on new warships commissioned from 1914 onwards by the QF 4-inch Mk V. This new generation of warships were more heavily armed, and the BL Mk VII's role as secondary armament on capital ships and primary armament on cruisers was taken over by the BL 6-inch Mk VII and BL 6-inch Mk XII while the 4-inch calibre became the secondary armament on cruisers and primary armament on destroyers.

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

World War I field gun service

A battery of 4 guns mounted on field carriages was first deployed with the South African Heavy Artillery in the German South West Africa campaign in 1915 and returned to England in September. They were then deployed in the East African Campaign from February 1916 with 11th Heavy Battery (renumbered 15th Battery from April 1916) manned by the Royal Marine Artillery.^[8]

Surviving examples

• 2 Mk VII guns from HMS New Zealand outside the Auckland War Memorial Museum

See also

• List of naval guns

Weapons of comparable role, performance and era

• 4"/50 caliber gun US equivalent

Sources

• HANDBOOK for the 4" Mark VII. and VIII. B.L. Guns 1913 (Corrected to September 1913.) ADMIRALTY Gunnery Branch, G.8652/13
• Campbell . John . Lambert, Andrew D. . 1987 . British Naval Guns, 1880–1945, No. 17 . Warship . 10 . 53–55.
• DiGiulian, Tony. British 4"/50 (10.2 cm) BL Mark VII
• Farndale, General Sir Martin. History of the Royal Regiment of Artillery : Forgotten Fronts and the Home Base 1914–18. London:The Royal Artillery Institution, 1988
• Book: Naval Weapons of World War II . Campbell, John . Naval Institute Press . 1985 . 0-87021-459-4.

Notes and References

1. Campbell, Naval Weapons of WWII, p. 43.
2. HANDBOOK for the 4" Mark VII. and VIII. B.L. Guns 1913
3. 2852 ft/second firing a 31 lb 3 CRH projectile, using 9 lb 5 oz 15 drams cordite MD size 16 propellant. HANDBOOK for the 4" Mark VII. and VIII. B.L. Guns 1913.
4. Campbell, Warship Volume X, p. 53.
5. Campbell, Naval Weapons of WWII, p. 43.
6. Mk VII = Mark 7. Britain used Roman numerals to denote Marks (models) of ordnance until after World War II. Mark VII indicates this was the seventh model of BL 4-inch gun.
7. Campbell, Naval Weapons of WWII, p. 43.
8. Farndale 1988, page 318