page_title: RML 9-inch 12-ton gun
section_title: Mk VI high-angle gun
hierarchical_section_title: RML 9-inch 12-ton gun / Mk VI high-angle gun
caption_attribution_description: Photograph showing six 10-inch RML high-angle coast-defence guns at Spy Glass Battery, Gibraltar.
context_page_description: The RML 9-inch guns Mark I – Mark VI were large rifled muzzle-loading guns of the 1860s used as primary armament on smaller British ironclad battleships and secondary armament on larger battleships, and also ashore for coast defence.
context_section_description: In the late 1880s and early 1890s a small number of guns were adapted as high-angle coast defence guns around Britain : 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.
caption: Spy Glass Battery, Gibraltar
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