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Ordnance RML 10 inch 18 ton gun
HMS Sultan (1870) 10-inch gun.jpg
Mk I gun on broadside ironclad HMS Sultan in the 1890s
Type Naval gun
Coast defence gun
Place of origin United Kingdom
Service history
In service 1868 - 19??
Used by Royal Navy
Australian Colonies
Wars Bombardment of Alexandria (1882)
Production history
Designer M Robert Fraser, Royal Gun Factory
Designed 1868
Manufacturer Royal Arsenal
Unit cost £1006[1]
Variants Mks I - II
Barrel length 145.5 inches (3.70 m) (bore)[2]

Shell 400 to 410 pounds (181.4 to 186.0 kg) Palliser, Common, Shrapnel
Calibre 10-inch (254.0 mm)
Muzzle velocity Palliser : 1,364 feet per second (416 m/s)
Common & shrapnel : 1,028 feet per second (313 m/s)[3]
Maximum range 6,000 yards (5,500 m)

The RML 10 inch guns Mk I - Mk II were large rifled muzzle-loading guns designed for British battleships and monitors. They were also fitted to the Bouncer-class flat-iron gunboats.[4]


Mk I & MK II gun barrels

The 10-inch gun was a standard "Woolwich" design (characterised by having a steel A tube with relatively few broad, rounded and shallow rifling grooves) developed in 1868, based on the successful Mk III 9-inch gun, itself based on the "Fraser" system. The Fraser system was an economy measure applied to the successful Armstrong design for heavy muzzle-loaders, which were expensive to produce. It retained the Armstrong steel barrel surrounded by wrought-iron coils under tension, but replaced the multiple thin wrought-iron coils shrunk around it by a single larger coil (10 inch Mark I) or 2 coils (Mark II); the trunnion ring was now welded to other coils; and it eliminated Armstrong's expensive forged breech-piece.[5]

The gun was rifled with 7 grooves, increasing from 1 turn in 100 calibres to 1 in 40.[2]

It was first used for the main armament on the central battery ironclad HMS Hercules, completed in late 1868.

A number of the Mk I guns on HMS Hercules and one of the two damaged guns in HMVS Cerberus suffered from cracked barrels.[6] Presumably this is why only a few (at least 25) Mk I guns were made.


When the gun was first introduced in 1868, projectiles had several rows of projecting "studs" which engaged with the gun's rifling to impart spin. From the mid-late 1870s, spin was imparted by "gas checks" connected to the base of the projectile which engaged the rifling grooves, making studs unnecessary, and hence the shells were designated "studless".

The gun's primary projectile was "Palliser" shot or shell, an early armour-piercing projectile for attacking armoured warships. A large "battering charge" of 70 pounds "P" (pebble) or 60 pounds "R.L.G." (rifle large grain) gunpowder[7] was used for the Palliser projectile to achieve maximum velocity and hence penetrating capability.

Common (i.e. ordinary explosive) shells and shrapnel shells were fired with the standard "full service charge" of 44 pounds "P" or 40 pounds R.L.G. gunpowder,[7] as for these velocity was not as important.

See also

Surviving examples

One of the guns on top of Fort St Catherine, Bermuda

One 10 inch Mk I Common Shell, one 10 inch Mk II Common Shell & one 10 inch Mk III Palliser Shot as part of the Victorian Navy display at the Geelong Maritime Museum, Australia. Details

Various other guns are mounted or unmounted in Bermuda, with some lying outside of Fort St Catherine, having been rolled out when made obsolete, and a number having been found buried in the moat of Fort Cunningham (the two mounted at Fort George are the RML 11 inch 25 ton gun). At least one has been erected on a display stand at Fort Hamilton, though the original mount is missing, and another at Alexandia Battery.

Notes and references

  1. Unit cost of £1005 10 shillings 2 pence is quoted in "The British Navy" Volume II, 1882, by Sir Thomas Brassey. Page 38
  2. 2.0 2.1 Treatise on Construction of Service Ordnance 1877, page 292
  3. 1,364 feet/second firing 400-pound projectile with "Battering charge" of 70 pound "P" (gunpowder). Treatise on Construction of Service Ordnance 1877, page 348. 1,028 feet/second firing 410-pound common shell with gas-check with 44 pounds "P" (gunpowder). Victorian Navy Handbook 1887, page 211.
  4. Paloczi-Horvath, George (1996). From Monitor to Missile Boat Coast Defence Ships and Coastal Defence since 1860. Conway Maritime Press. p. 27. ISBN 0-85177-650-7. 
  5. Treatise on Construction of Service Ordnance 1877, page 92-93
  6. HMVS Cerberus website. reports of cracked guns
  7. 7.0 7.1 Treatise on Ammunition 1877, page 220


External links

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