BL 4 inch naval gun Mk I – VI

Ordnance BL 4 inch gun Mk I - Mk VI

Type	Naval gun
Place of origin	United Kingdom
Service history
In service	1880s - 190?
Used by	United Kingdom
Specifications
Barrel length	Mk I 22.5cwt : 100 inches (2.540 m) bore (25 calibres)^[1] Mk II - VI : 108 inches (2.743 m) bore (27 calibres)^[2] 120 inches total^[1]

Shell	25 pounds (11.34 kg)^[2]
Calibre	4-inch (101.6 mm)
Breech	3-motion screw
Muzzle velocity	Mk I 13cwt : 1,180 feet per second (360 m/s)^[3] Mk II - VI : 1,900 feet per second (580 m/s)^[4]
Maximum firing range	Mk II-VI 7,700 yards (7,000 m)^[2]

The BL 4-inch gun Mk I - Mk VI^[5] were a family of early British breech-loading 4-inch naval guns.

History

13 cwt Mk I, 15 calibres

This was the first 4-inch BL gun. With its short (60-inch total) barrel it had a range of only 5,500 yards.^[1]

22.5 cwt Mk I, 25 calibres

With its longer barrel (100 inch bore) Mk I had a range of 7,200 yards.^[1] Both early Mk I types were quickly withdrawn from service following the explosion of a similar BL 6 inch Mk II gun on board HMS Cordelia in June 1891.^[1] Mk I 22.5 cwt continued to be used for training.

26 cwt Mks II - VI, 27 calibres

The improved 27-calibres Mk II gun and subsequent Marks, often referred to as 4 inch 26 cwt, replaced the early Mk I versions in service. The longer barrel (108 inch bore : 27 calibres) gave it a range of 7,700 yards.^[6]

Mk II guns and later Marks armed the following warships :

HMS Inflexible as re-gunned in 1885
HMS Bellerophon as re-gunned in 1885
Pygmy class composite screw gunboats of 1888
Redbreast-class gunboats launched in 1889
HMS Alexandra as re-gunned in 1891
Alert-class sloops of 1894

The gun was succeeded in its class from 1895 by the QF 4 inch gun Mk I.

QFC 4 inch gun

A small number of these guns were converted to QF to use the same cartridges as the QF 4 in gun. They were designated Mk I/IV, I/VI etc. depending on which Mark of BL 4-inch had been converted. All had a bore of 27.85 calibres after conversion, with a muzzle velocity of 2,177 ft/second.^[2]

Surviving examples

A gun from 1888 at Explosion! The Museum of Naval Firepower, Gosport from Victorian Forts and Artillery website
A gun from HMS Gannet, mounted on top of Calshot Castle at the entrance to Southampton Water from Victorian Forts and Artillery website

Notes and references

1 2 3 4 5 DiGiulian
1 2 3 4 Text Book of Gunnery, 1902
↑ Mk I 13cwt gun : 1180 ft/sec firing 25 pound projectile with 3lb 4oz RLG2 (gunpowder). Text Book of Gunnery 1887, Table XVI page 313
↑ Mk II - VI 1,900 ft/s with 25 lb (11 kg) projectile, using 12 lb (5.4 kg) S.P. (gunpowder) or 3 lb 1 oz (1.4 kg) cordite MK I size 5 propellant (Text Book of Gunnery, 1902)
↑ Mk I - Mk VI = Marks 1 through to Mark 6. Britain used Roman numerals to denote Marks (models) of ordnance until after World War 2. This article covers the first six models of British BL 4-inch naval guns
↑ Text Book of Gunnery 1902

Bibliography

External links

Handbook of the 4-inch Gun Marks V and VI. (Land Service.) 1904

Wikimedia Commons has media related to BL 4 inch Mk I - VI naval gun.

British Empire naval weapons of the Victorian era

Smoothbore muzzle-loading cannons	18-pounder 24-pounder 32-pounder 58 cwt 68-pounder Somerset cannon

Smoothbore muzzle-loading shell guns	8 inch 10-inch 86 cwt

Mortars	10-inch Blomefield 13-inch Blomefield

Howitzers	12-pounder Millar 24-pounder Millar

Rifled breechloaders (Armstrong)	RBL 9 pounder RBL 20 pounder RBL 40 pounder RBL 7 inch 110 pounder

Rifled muzzle-loaders (Lancaster)	68-Pounder Lancaster gun

Rifled muzzle-loaders (converted)	RML 64 pounder 71 cwt

Rifled muzzle-loaders (Woolwich)	RML 9 pounder 8 cwt RML 64 pounder 64 cwt RML 7 inch RML 8 inch RML 9 inch RML 10 inch RML 11 inch RML 12 inch 25 ton RML 12 inch 35 ton RML 12.5 inch RML 16 inch

Quick-firing guns	QF 3-pounder Hotchkiss QF 6-pounder Hotchkiss QF 6 pounder Nordenfelt QF 12-pounder 12 cwt Mk I QF 4 inch QF 4.7 inch QF 6 inch

Breech-loaders (new pattern)	BL 4 inch BL 5 inch BL 6 inch 80 pounder BL 6 inch Mk II – VI BL 8 inch BL 9.2 inch Mk I – VII BL 9.2 inch Mk VIII BL 10 inch BL 12 inch Mk I – VII BL 12 inch Mk VIII BL 13.5 inch BL 16.25 inch

Light weapons	Gatling gun Gardner gun Nordenfelt gun 1-inch Nordenfelt gun

Torpedoes	Whitehead torpedo

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