BL 4-inch Mk I–VI naval gun
| 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With its longer barrel (100 inch bore) Mk I had a range of 7,200 yards.[1] Both early Mk I types were quickly withdrawn from service following the explosion of a similar BL 6 inch Mk II gun on board HMS Cordelia in June 1891.[1] Mk I 22.5 cwt continued to be used for training.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-calibre 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-inch 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
See also
Notes and references
- ^ a b c d e DiGiulian
- ^ a b c d 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
- Text Book of Gunnery, 1887. LONDON : PRINTED FOR HIS MAJESTY'S STATIONERY OFFICE, BY HARRISON AND SONS, ST. MARTIN'S LANE Archived 4 December 2012 at archive.today
- Text Book of Gunnery, 1902. LONDON : PRINTED FOR HIS MAJESTY'S STATIONERY OFFICE, BY HARRISON AND SONS, ST. MARTIN'S LANE Archived 12 July 2012 at archive.today
- Tony DiGiulian, British Early 4" (10.2 cm) Breech Loaders