{{Infobox weapon | name = RML 7-inch gun | image = RML 7-inch gun and crew HMS Minotaur.jpg | image_size = 300 | caption = 7-inch 6½ ton Mk I gun and crew on {{HMS|Minotaur|1863|6}} | origin = United Kingdom | type = Naval gun<br />Coast defence gun <!-- Type selection --> | is_ranged = YES | is_bladed = | is_explosive = | is_artillery = YES | is_vehicle = | is_UK = YES <!-- Service history --> | service = | used_by = Royal Navy | wars = <!-- Production history --> | designer = Royal Gun Factory | design_date = 1865 (7 & 6½ ton)<br />1874 (90 cwt) | manufacturer = Royal Arsenal | production_date = | number = | unit_cost = £425<ref>Unit cost of £424 11 shillings 10 pence is quoted for the 7-inch 6½ ton gun in "The British Navy" Volume II, 1882, by Sir Thomas Brassey. Page 38</ref> | variants = 7 ton Mks I – IV<br />6½ ton Mks I – III<br />90 cwt <!-- General specifications --> | weight = | length = | part_length = 7 ton : {{convert|126|in|mm}}<br />6½ ton & 90 cwt : {{convert|111|in|mm}}<ref name="ReferenceA">Treatise on construction of ordnance in the British service, 1877, Table XXIX</ref> | width = | height = | crew = <!-- Ranged weapon specifications --> | cartridge = {{convert|112|to|115|lb|kg}} Palliser, Common, Shrapnel<ref>Treatise on Ammunition 1877 and Treatise on construction of ordnance in the British service, 1877 describe a 115-pound projectile; Text Book of Gunnery 1887 and Brassey's Naval Annual 1888 describe a 112-pound 1 oz projectile. 112 lb 1 oz appears to be the weight of the empty Palliser shell i.e. without gunpowder filling which was typically 2 lb 10 oz. By 1887 palliser shell had been discontinued and existing shell converted to shot by removing the gunpowder – hence old Palliser ammunition would then be 112 lb 1 oz.</ref><br />{{convert|160|lb|kg}} double common shell | caliber = {{convert|7|in|mm|sing=on|sigfig=4}} | action = | rate = | velocity = 7 ton : {{convert|1561|ft/s|m/s}}<br />6½ ton : {{convert|1525|ft/s|m/s}}<br />90 cwt : {{convert|1325|ft/s|m/s}} | range = | max_range = {{convert|5500|yd|m}} | feed = | sights = <!-- Artillery specifications --> | breech = | recoil = | carriage = | elevation = | traverse = }} The '''RML 7-inch guns''' were various designs of medium-sized rifled muzzle-loading guns used to arm small to medium-sized British warships in the late 19th century, and some were used ashore for coast defence.
== Design and history == [[File:Woolwich rifling diagram.jpg|thumb|left|{{center|"Woolwich" rifling introduced in 1865}}]] These guns were the first to incorporate the new "Woolwich" rifling system, a modification of the French system, of from 3 – 9 broad shallow grooves after Britain abandoned the Armstrong "shunt" rifling system in May 1865 : "...M.L. {{convert|7|in|cm|abbr=on}} guns in course of manufacture were rifled on this principle, upon which all of our heavy pieces since have been rifled. The {{convert|7|in|cm|abbr=on}} referred to, and introduced into the service in 1865, were the first of the so-called Woolwich guns, which then meant "''wrought iron M.L. guns built up on Sir W. Armstrong's principle, improved upon by hooking the coils over one another, and having solid ended steel barrels, rifled on the system shown above, for studded projectiles''".<ref>Treatise on construction of ordnance in the British service, 1877, Page 91</ref>
All versions were constructed of a steel A tube surrounded by various numbers and thicknesses of wrought-iron coils. Rifling was 3 grooves with a uniform 1 turn in 35 calibres i.e. in {{convert|245|in|cm|abbr=on}}.<ref name="ReferenceA" />
The diagrams below show the progression from the original expensive Armstrong construction in Mk I of multiple relatively thin coils, through to the simplified and cheaper Woolwich design of Mk III. <gallery widths=180> RML 7-inch 7 ton gun diagrams.jpg|{{center|The 4 Marks of 7 ton gun}} RML 7-inch 6½ ton gun diagrams.jpg|{{center|The 3 Marks of 6½ ton gun}} RML 7-inch 90 cwt gun diagrams.jpg|{{center|90 cwt gun}} </gallery>
=== RML 7-inch 7 ton gun === [[File:Flat Holm Canon.jpg|thumb|left|{{center|Remains of a 7-ton Mk III gun on Flat Holm island, UK}}]] This was a coast defence gun introduced in 1865 to replace the failed RBL 7-inch Armstrong gun.Three marks were produced. {{clearleft}}
=== RML 7-inch 6½ ton gun === This was a naval gun introduced in 1865 "...as a broadside or pivot gun for frigates, to replace the 7-inch B.L. and 68-pr S.B. guns, and is now very extensively used, 331 having been made... These guns are in total length {{convert|18|in|cm|abbr=on}} shorter than the land service [i.e. 7-ton] {{convert|7|in|cm|abbr=on}} gun, being a length more suited to the requirements of the Navy".<ref>Treatise on construction of ordnance in the British service, 1877, Page 269</ref> Some sources credit these weapons with the ability to pierce up to {{convert|7.7|in|0}} of armour.<ref>Conway's All the World's Fighting Ships 1860-1905, 1979, Page 9</ref>
The following warships were armed with the gun : * {{sclass|Amazon|sloop|1}}s in commission from 1865 * {{HMS|Bellerophon|1865|6}} commissioned in 1866 * {{HMS|Vixen|1865|6}} commissioned 1866 * {{HMS|Viper|1865|6}} commissioned 1866 * {{sclass|Minotaur|ironclad|1}}s commissioned 1867 * {{sclass|Eclipse|sloop|1}}s in commission from 1867 * {{sclass|Defence|ironclad|1}}s (as re-gunned in 1867) * {{HMS|Enterprise|1864|6}} & {{HMS|Research|1863|6}} (as re-gunned in 1868) * {{sclass|Warrior|ironclad|1}}s (as re-gunned in 1867–1868) * {{sclass|Hector|ironclad|1}}s (from 1868) * {{HMS|Achilles|1863|6}} (as re-gunned in 1868) * {{HMS|Inconstant|1868|6}} in commission from 1869 * {{HMS|Shah|1873|6}} in commission from 1876 * ''Briton''-class screw corvettes in commission from 1871
=== RML 7-inch 90 cwt gun === This was a lighter (90 cwt = 4½ tons) low-powered naval gun introduced in 1874 as a broadside gun on unarmoured vessels, and not intended for attacking armour plate. Early models were made by simply turning off some of the jacket around {{convert|7|in|cm|abbr=on}} 6½ ton guns, as firing with reduced charges placed less strain on the coils. Some new guns were made to similar design.
The following warships were armed with the gun : * {{sclass|Osprey|sloop}}s in commission from 1874 * {{HMS|Raleigh|1873|6}} in commission from 1874 * {{sclass|Fantome|sloop|1}}s in commission from 1874 * {{sclass|Bacchante|corvette|1}}s in commission from 1877 * {{sclass|Condor|gunvessel|1}}s in commission from 1877
== Ammunition == The primary projectile for 7 ton and 6½ ton guns was Palliser shot or shell for attacking armoured warships, fired with a large "battering" charge for maximum velocity. All guns were also equipped with shrapnel shells for anti-personnel use and explosive common shells for attacking unarmoured targets. The "double" common shell was much longer than the standard common shell, and hence contained approximately twice as much gunpowder. It was unstable in flight and hence inaccurate beyond {{convert|2000|yd|km|abbr=on}} but was considered useful for attacking wooden warships at ranges below {{convert|2000|yd|km|abbr=on}}.<ref>Treatise on Ammunition 1877, Page 189</ref> <gallery heights=180> RML 7-inch Palliser shell Mk III diagram.jpg|{{center|Mk III Palliser shell}} RML 7-inch Palliser shot Mk VI diagram.jpg|{{center|Mk VI Palliser shot}} RML 7-inch Mk III shrapnel shell diagram.jpg|{{center|Mk III shrapnel shell}} RML 7-inch Mk V common shell diagram.jpg|{{center|Mk V common shell}} RML 7-inch Mk III double common shell diagram.jpg|{{center|Mk III double common shell}} </gallery>
This was the only RML heavy gun not to be issued with gas-checks.
== Surviving examples == * Restored [https://www.flickr.com/photos/9977224@N06/1490513479 6½ ton Mk I Numbers 148 & 163] at Garden Island Rockingham, Western Australia (Fleet Base West). For restoration story see http://www.defence.gov.au/news/navynews/editions/4719/feature/feature06.htm * [http://www.palmerstonforts.org.uk/art/gallery1/large/ascn03.jpg Several 6½ ton Mk I guns on Ascension Island] * 6½ ton Mk I at Fort Siloso, Singapore * [https://www.flickr.com/photos/9977224@N06/1374682442 6½ ton Mk III of 1869, at Elizabeth Castle, Jersey, UK] * Remains of several 7 ton Mk III guns on Flat Holm island, UK * Nine 7 ton Mk III guns on Steep Holm island, UK * A 7-ton Mk I gun at The Citadel, Nova Scotia, Canada * A 6½ ton Mk I gun on Signal Hill (Cape Town), South Africa.
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== See also == * List of naval guns
== Notes and references == {{reflist}}
== Bibliography == * [https://archive.org/details/treatiseonconst00offigoog Treatise on the construction and manufacture of ordnance in the British service. War Office, UK, 1877] * [http://download404.mediafire.com/lwwy9ytbtzeg/5zhwmwn41lg/Treatise+on+ammunition+1877.pdf Treatise on Ammunition. War Office, UK, 1877]{{dead link|date=April 2018 |bot=InternetArchiveBot |fix-attempted=yes }} * [http://www.victorianforts.co.uk/art/gun2.htm#rml Victorian Forts Website. Rifled Muzzle Loading Guns] {{Webarchive|url=https://web.archive.org/web/20160303211534/http://www.victorianforts.co.uk/art/gun2.htm#rml |date=2016-03-03 }} * Sir Thomas Brassey, [https://archive.org/details/britishnavyitss04brasgoog The British Navy, Volume II. London: Longmans, Green and Co. 1882] * [http://cgsc.cdmhost.com/u?/p4013coll11,222 Text Book of Gunnery, 1887. LONDON : PRINTED FOR HIS MAJESTY'S STATIONERY OFFICE, BY HARRISON AND SONS, ST. MARTIN'S LANE] {{Webarchive|url=https://archive.today/20121204140418/http://cgsc.cdmhost.com/u?/p4013coll11,222 |date=2012-12-04 }} * [https://archive.org/details/brasseysannual00brasgoog Brassey's Naval Annual, 1888] * {{cite book|title=Conway's All the World's Fighting Ships 1860-1905|editor1-last=Chesneau|editor1-first=Roger|editor2-last=Kolesnik|editor2-first=Eugene M.|publisher=Conway Maritime Press|location=Greenwich, UK|year=1979|isbn=0-8317-0302-4|name-list-style=amp|url-access=registration|url=https://archive.org/details/conwaysallworlds0000unse_l2e2}}
== External links == {{Commons category|RML 7 inch gun}} * [http://handle.slv.vic.gov.au/10381/104174 Handbook for the 7-inch R.M.L. guns of 6½ and 7 tons on sliding and Moncrieff carriage land service, 1888] at State Library of Victoria * [http://www.victorianforts.co.uk/art/mon3.htm Diagram showing 7 ton Mk III gun on Moncrieff mounting Mk I] {{Webarchive|url=https://web.archive.org/web/20160303224802/http://www.victorianforts.co.uk/art/mon3.htm |date=2016-03-03 }} * [http://www.victorianforts.co.uk/art/mon5.htm Diagram showing 7 ton Mk III gun on Moncrieff mounting Mk II] {{Webarchive|url=https://web.archive.org/web/20160303233122/http://www.victorianforts.co.uk/art/mon5.htm |date=2016-03-03 }}
{{VictorianEraBritishNavalWeapons}} {{VictorianEraBritishWeapons}}
{{DEFAULTSORT:RML 07-inch gun}} Category:Artillery of the United Kingdom Category:Naval guns of the United Kingdom Category:178 mm artillery Category:Victorian-era weapons of the United Kingdom Category:Coastal artillery Category:175 mm artillery