RML 9 inch 12 ton gun
Encyclopedia
The RML 9 inch guns Mark I - Mark VI were large rifled muzzle-loading guns used as primary armament on smaller British ironclad battleships and secondary armament on larger battleships, and also ashore for coast defence.
Mark I, introduced in 1865, incorporated the strong but expensive Armstrong
method of a steel A tube surrounded by multiple thin wrought-iron coils which maintained the central A tube under compression, and a forged steel breech-piece. 190 were made.
Mark II in 1866 incorporated the modified "Fraser" design. This was an economy measure, intended to reduce the costs incurred in building to the Armstrong design. It incorporated fewer but heavier wrought-iron coils but retained the Armstrong forged breech-piece. Only 26 were made.
Mark III in 1866-1867 eliminated the Armstrong forged breech piece and hence fully implemented the Fraser economy design. It consisted of only 4 parts : steel A tube, cascabel, B tube and breech coil. 136 were made.
Mark IV, introduced 1869, and V incorporated a thinner steel A tube and 2 breech coils. The explanation for separating the heavy breech coil of Mk III into a coiled breech piece covered by a breech coil was "the difficulty of ensuring the soundness of the interior of a large mass of iron".
In the late 1880s and early 1890s a small number of guns were adapted as high-angle coast defence guns around England : known battery locations were Tregantle Down Battery at Plymouth, Verne High Angle Battery at Portland
and Steynewood Battery
at Bembridge on the Isle of Wight
.
The idea behind these high-angle guns was that the high elevation gave the shell a steep angle of descent and hence enabled it to penetrate the lightly armoured decks of attacking ships rather than their heavily armoured sides. To increase accuracy the old barrels were relined and given modern "polygroove" rifling : 27 grooves with a twist increasing from 1 turn in 100 calibres to 1 turn in 35 calibres after 49.5 inches. These guns fired a special 360-pound armour-piercing shell to a range of 10,500 yards using a propellant charge of 14 lb Cordite Mk I size 7½, remained in service through World War I
and were not declared obsolete until 1922.
Some guns were bored out and relined in 10-inch calibre. A battery of six such guns is known to have been mounted at Spy Glass Battery on the rock of Gibraltar, and six guns at Gharghur, Malta.
The gun's primary projectile was "Palliser" shot or shell
, an early armour-piercing projectile for attacking armoured warships. A large "battering charge" of 50 pounds "P" (pebble) or 43 pounds "R.L.G." (rifle large grain) gunpowder 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 30 pounds R.L.G. gunpowder or 33 pounds P (pebble) gunpowder, as for these velocity was not as important.
Design
The rifling was the "Woolwich" pattern of a relatively small number of broad, rounded shallow grooves : there were 6 grooves, increasing from 0 to 1 turn in 45 calibres (i.e. 405 inches).Mark I, introduced in 1865, incorporated the strong but expensive Armstrong
William George Armstrong, 1st Baron Armstrong
William George Armstrong, 1st Baron Armstrong CB, FRS was an effective Tyneside industrialist who founded the Armstrong Whitworth manufacturing empire.-Early life:...
method of a steel A tube surrounded by multiple thin wrought-iron coils which maintained the central A tube under compression, and a forged steel breech-piece. 190 were made.
Mark II in 1866 incorporated the modified "Fraser" design. This was an economy measure, intended to reduce the costs incurred in building to the Armstrong design. It incorporated fewer but heavier wrought-iron coils but retained the Armstrong forged breech-piece. Only 26 were made.
Mark III in 1866-1867 eliminated the Armstrong forged breech piece and hence fully implemented the Fraser economy design. It consisted of only 4 parts : steel A tube, cascabel, B tube and breech coil. 136 were made.
Mark IV, introduced 1869, and V incorporated a thinner steel A tube and 2 breech coils. The explanation for separating the heavy breech coil of Mk III into a coiled breech piece covered by a breech coil was "the difficulty of ensuring the soundness of the interior of a large mass of iron".
Mk VI high-angle gun
Isle of Portland
The Isle of Portland is a limestone tied island, long by wide, in the English Channel. Portland is south of the resort of Weymouth, forming the southernmost point of the county of Dorset, England. A tombolo over which runs the A354 road connects it to Chesil Beach and the mainland. Portland and...
and Steynewood Battery
Steynewood Battery
Steynewood Battery is a battery located between Bembridge and Whitecliff Bay on the Isle of Wight. It is one of the many Palmerston Forts built on the island to protect it in response to a perceived French invasion. Construction of the battery began in 1889 and was completed by 1893....
at Bembridge on the Isle of Wight
Isle of Wight
The Isle of Wight is a county and the largest island of England, located in the English Channel, on average about 2–4 miles off the south coast of the county of Hampshire, separated from the mainland by a strait called the Solent...
.
The idea behind these high-angle guns was that the high elevation gave the shell a steep angle of descent and hence enabled it to penetrate the lightly armoured decks of attacking ships rather than their heavily armoured sides. To increase accuracy the old barrels were relined and given modern "polygroove" rifling : 27 grooves with a twist increasing from 1 turn in 100 calibres to 1 turn in 35 calibres after 49.5 inches. These guns fired a special 360-pound armour-piercing shell to a range of 10,500 yards using a propellant charge of 14 lb Cordite Mk I size 7½, remained in service through World War I
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...
and were not declared obsolete until 1922.
Some guns were bored out and relined in 10-inch calibre. A battery of six such guns is known to have been mounted at Spy Glass Battery on the rock of Gibraltar, and six guns at Gharghur, Malta.
Ammunition
When the gun was first introduced in 1865, 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
Palliser shot
Palliser shot was invented by Sir William Palliser and hence its name. It was an early British armour-piercing artillery projectile, intended to pierce the armour protection of warships being developed in the second half of the 19th century.-History:...
, an early armour-piercing projectile for attacking armoured warships. A large "battering charge" of 50 pounds "P" (pebble) or 43 pounds "R.L.G." (rifle large grain) gunpowder 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 30 pounds R.L.G. gunpowder or 33 pounds P (pebble) gunpowder, as for these velocity was not as important.
Surviving examples
- Needles Old Battery, Isle of Wight, UK
- A gun from the Needles Old Battery, now outside Southsea Castle, Portsmouth, UK
- Hurst CastleHurst CastleHurst Castle on the south coast of England is one of Henry VIII's Device Forts, built at the end of a long shingle barrier beach at the west end of the Solent to guard the approaches to Southampton. Hurst Castle was sited at the narrow entrance to the Solent where the ebb and flow of the tides...
, UK - Mk V No. 592 at South HeadSouth HeadSouth Head may mean:* The south head of Port Jackson, New South Wales, Australia; one of the Sydney Heads* South Head at the entrance to Wick Bay on the northeast coast of Scotland....
, Sydney, Australia - MK I No. 1670 of 1867 at Fort QueenscliffFort QueenscliffFort Queenscliff, in Victoria, Australia, dates from 1860 when an open battery was constructed on Shortland's Bluff to defend the entrance to Port Phillip. The Fort, which underwent major redevelopment in the late 1870s and 1880s, became the headquarters for an extensive chain of forts around Port...
, Victoria, Australia - No.s 1679 & 1683 at The Strand, Williamstown, Victoria, Australia
- No.s 1669 & 1675 at Fort Gellibrand, Victoria, Australia
- Mk V gun of 1872 at Whampoa, Kowloon, Hong Kong
- At York Redoubt National Historic Site, Halifax, Nova Scotia, Canada
External links
- Diagram of gun on Moncrieff disappearing mounting, at Palmerston Forts Society website
- Diagram of gun on Casemate "A" Pivot mounting, at Palmerston Forts Society website
- Diagram of gun on "C" Pivot, at Palmerston Forts Society website
- Diagram of gun on Dwarf "A" Pivot, at Palmerston Forts Society website
- Diagram of gun on High Angle mounting, at Palmerston Forts Society website