RML 8-inch 9-ton gun

The British RML 8-inch 9-ton guns Mark I – Mark III[5] were medium rifled muzzle-loading guns used to arm smaller ironclad warships and coast defence batteries in the later 19th century.

RML 8-inch 9-ton gun
TypeNaval gun
Coast defence gun
Place of originUnited Kingdom
Service history
In service1866–190?
Used byRoyal Navy
Production history
ManufacturerRoyal Arsenal
Unit cost£568[1]
VariantsMk I – Mk III
Mass9 long tons (9.1 t)
Barrel length118 inches (3.0 m) bore + chamber[2]

Shell174 pounds 12 ounces (79.3 kg)[3]
Calibre8-inch (203.2 mm)
Muzzle velocity1,420 feet per second (430 m/s)[4]


In common with other Royal Ordnance RML designs of the 1860s, Mark I used the strong but expensive Armstrong system of a steel tube surrounded by a complex system of multiple wrought-iron coils, which was progressively simplified in Marks II and III to reduce costs : Mark III consisted only of A tube, B tube, breech coil and cascabel screw.

Rifling was of the "Woolwich" pattern of a small number of broad shallow grooves: 4 grooves with twist increasing from 0 to 1 turn in 40 calibres (i.e. in 320 inches) at the muzzle.


The ammunition was mainly studded, with the studs engaging in the Woolwich rifling grooves. However, a studless pointed common shell with automatic gas-check also became available later in the gun's life.[6]

See also

Surviving examples

Notes and references

  1. Unit cost of £567 12 shillings 10 pence is quoted in "The British Navy" Volume II, 1882, by Sir Thomas Brassey. Page 38
  2. Text Book of Gunnery 1887 Table XVI page 313
  3. 174 lb 12 oz projectile. Text Book of Gunnery 1887 Table XVI page 313
  4. 1,420 feet/second firing 174-pound 12-oz projectile . Text Book of Gunnery 1887 Table XVI page 313
  5. Mark I – Mark III = Mark 1 through to Mark 3. Britain used Roman numerals to denote Marks (models) of ordnance until after World War II. Hence this article describes the three models of RML 8-inch guns.
  6. Gas-checks in British RML heavy guns


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