|Ordnance BL 4 inch gun Mk I - Mk VI|
|Place of origin||United Kingdom|
|In service||1880s - 190?|
|Used by||United Kingdom|
|Barrel length||Mk I 22.5cwt : 100 inches (2.540 m) bore (25 calibres)|
Mk II - VI : 108 inches (2.743 m) bore (27 calibres) 120 inches total
|Shell||25 pounds (11.34 kg)|
|Calibre||4-inch (101.6 mm)|
|Muzzle velocity||Mk I 13cwt : 1,180 feet per second (360 m/s) Mk II - VI : 1,900 feet per second (580 m/s)|
|Maximum range||Mk II-VI 7,700 yards (7,000 m)|
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.
22.5 cwt Mk I, 25 calibres
With its longer barrel (100 inch bore) Mk I had a range of 7,200 yards. Both early Mk I types were quickly withdrawn from service following the explosion of a similar BL 6 inch Mk II gun on board HMS Cordelia in June 1891. 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.
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.
- 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
- 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
- Text Book of Gunnery, 1887. LONDON : PRINTED FOR HIS MAJESTY'S STATIONERY OFFICE, BY HARRISON AND SONS, ST. MARTIN'S LANE
- Text Book of Gunnery, 1902. LONDON : PRINTED FOR HIS MAJESTY'S STATIONERY OFFICE, BY HARRISON AND SONS, ST. MARTIN'S LANE
- Tony DiGiulian, British Early 4" (10.2 cm) Breech Loaders
|Wikimedia Commons has media related to BL 4 inch Mk I - VI naval gun.|
- Mk V or VI gun as movable fortification gun, on siege overbank carriage. At Victorian Forts and Artillery website
- Mk I diagram and photos at Victorian Forts and Artillery website
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