BL 9.2 inch gun Mk I–VII
| Ordnance BL 9.2 inch gun Mk I – Mk VII | |
|---|---|
Mk VI gun on disappearing mounting at Ben Buckler Gun Battery, Sydney
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|
| Type |
Naval gun Coast defence gun |
| Place of origin | United Kingdom |
| Service history | |
| In service | 1881–1918 |
| Used by |
Royal Navy Australian colonies |
| Wars | World War I |
| Production history | |
| Variants | Mk I – VII |
| Specifications | |
| Weight |
Mk I & II : 20 tons barrel & breech |
| Barrel length |
Mk I & II : 230 inches (5,842 mm) bore & chamber (25 calibres) |
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|
|
| Shell | 380 pounds (172.37 kg) 290 pounds (131.54 kg) (High-angle guns) |
| Calibre | 9.2-inch (233.7 mm) |
| Muzzle velocity | 2,065 feet per second (629 m/s) |
| Maximum firing range | 10,000 yards (9,100 m) |
Mk I & II : 20 tons barrel & breech
Mk III : 24 tons
Mk I & II : 230 inches (5,842 mm) bore & chamber (25 calibres)
The BL 9.2 inch guns Mk I – Mk VII were a family of early British heavy breechloading naval and coast defence guns in service from 1881 to the end of World War I. They were originally designed to use the old gunpowder propellants.
British 9.2 inch guns originated from a request by the Admiralty in 1879 for a gun comparable to Krupp's 24 cm (9.45 inch) gun at the time. The Admiralty submitted its request to the Committee on Ordnance, which was considering returning to breech-loading artillery after Britain's brief return to muzzle-loaders in the 1860s and 1870s. A new breech-loading gun with a 9.2 inch (234 mm) bore, firing a 380-pound projectile was calculated to be suitable. A total of 19 Mk I and Mk II guns of 26 calibres were made starting in 1881, but after lengthy delays and modifications still proved unsatisfactory; none made it to sea.
The 31.5 calibres versions, Mk III through to Mk VII became the first to be mounted on ships and deployed in general service.
Guns equipped the following ships :
Most Mk IV guns and some Mk VI guns were used in coast defences.
In the mid-to-late 1880s successful trials were carried out with RML 9-inch coast-defence guns firing at high angles in order to test the effectiveness of plunging fire on decks of ships. When surplus BL 9.2 inch Mk IV and Mk VI guns became available in the 1890s they were likewise adapted to high-angle carriages, with their obsolete 3-motion breech mechanisms replaced by modern continuous-motion patterns to allow faster loading. Locations included Plymouth and Gibraltar.
The elevation of up to 45° meant that the shell was at risk of slipping back after being rammed forward; only the copper driving band held the shell in place in a BL gun, and they had not been designed to operate at such high angles. The solution adopted was to develop a special high-angle reduced-charge cartridge with a hollow up the centre, through which the gunner inserted a 1 1⁄4-inch-diameter (32 mm) stick about 40 inches long made of beech wood, to prevent the projectile from slipping back before firing. A "light" 290-pound (130 kg) shell was used for high-angle firing, rather than the standard 380-pound (170 kg) shell.
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Wikipedia