page_title: RML 10-inch 18-ton gun
section_title: Design
hierarchical_section_title: RML 10-inch 18-ton gun / Design
caption_attribution_description: Diagrams showing construction of British RML 10 inch 18 ton gun Mk I and Mk II.
context_page_description: The RML 10-inch guns Mk I – Mk II were large rifled muzzle-loading guns designed for British battleships and monitors in the 1860s to 1880s. They were also fitted to the Bouncer and Ant-class flat-iron gunboats. They were also used for fixed coastal defences around the United Kingdom and around the British Empire until the early years of the 20th Century.
context_section_description: 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.
  The gun was rifled with 7 grooves, increasing from 1 turn in 100 calibres to 1 in 40.
  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. Presumably this is why only a few (at least 25) Mk I guns were made.
caption: Mk I & MK II gun barrels
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