| Ordnance BL 4-inch gun Mk I – Mk VI | |
| Origin: | United Kingdom |
| Type: | Naval gun |
| Is Ranged: | yes |
| Is Artillery: | yes |
| Is Uk: | yes |
| Service: | 1880s – 190? |
| Used By: | United Kingdom |
| Part Length: | Mk I 22.5cwt : 100inches bore (25 calibres)[1] Mk II – VI : 108inches bore (27 calibres) 120 inches total |
| Cartridge: | 25lb |
| Caliber: | 4sing=onNaNsing=on |
| Velocity: | Mk I 13cwt : 1180ft/s[2] Mk II – VI : 1900ft/s[3] |
| Max Range: | Mk II-VI 7700yd[4] |
| Breech: | 3-motion screw |
The BL 4-inch gun Mk I – Mk VI[5] were a family of early British breech-loading 4-inch naval guns.
This was the first 4-inch BL gun. With its short (60-inch total) barrel it had a range of only 5,500 yards.[6]
With its longer barrel (100 inch bore) Mk I had a range of 7,200 yards.Both early Mk I types were quickly withdrawn from service following the explosion of a similar BL 6 inch Mk II gun on board HMS Cordelia in June 1891.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.
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.[7]
Mk II guns and later Marks armed the following warships :
The gun was succeeded in its class from 1895 by the QF 4-inch gun Mk I.
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.
