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

These guns were the first to incorporate the new "Woolwich"

rifling Rifling is the term for helical grooves machined into the internal surface of a firearms's barrel for imparting a spin to a projectile to improve its aerodynamic stability and accuracy. It is also the term (as a verb) for creating such groov ...

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. guns in course of manufacture were rifled on this principle, upon which all of our heavy pieces since have been rifled. The 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''". All versions were constructed of a steel A tube surrounded by various numbers and thicknesses of

wrought-iron Wrought iron is an iron alloy with a very low carbon content (less than 0.05%) in contrast to that of cast iron (2.1% to 4.5%), or 0.25 for low carbon "mild" steel. Wrought iron is manufactured by heating and melting high carbon cast iron in an ...

coils. Rifling was 3 grooves with a uniform 1 turn in 35 calibres i.e. in . 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. RML 7-inch 7 ton gun diagrams.jpg, RML 7-inch 6½ ton gun diagrams.jpg, RML 7-inch 90 cwt gun diagrams.jpg,

RML 7-inch 7 ton gun

This was a coast defence gun introduced in 1865 to replace the failed RBL 7-inch Armstrong gun.Three marks were produced.

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 shorter than the land service .e. 7-ton gun, being a length more suited to the requirements of the Navy". Some sources credit these weapons with the ability to pierce up to of armour. The following warships were armed with the gun : * s in commission from 1865 * commissioned in 1866 * commissioned 1866 * commissioned 1866 * s commissioned 1867 * s in commission from 1867 * s (as re-gunned in 1867) * & (as re-gunned in 1868) * s (as re-gunned in 1867–1868) * s (from 1868) * (as re-gunned in 1868) * in commission from 1869 * 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 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 : * s in commission from 1874 * in commission from 1874 * s in commission from 1874 * s in commission from 1877 * 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 shell Shrapnel shells were anti-personnel artillery munitions that carried many individual bullets close to a target area and then ejected them to allow them to continue along the shell's trajectory and strike targets individually. They relied almost ...

s 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 but was considered useful for attacking wooden warships at ranges below .Treatise on Ammunition 1877, Page 189 RML 7-inch Palliser shell Mk III diagram.jpg, RML 7-inch Palliser shot Mk VI diagram.jpg, RML 7-inch Mk III shrapnel shell diagram.jpg, RML 7-inch Mk V common shell diagram.jpg, RML 7-inch Mk III double common shell diagram.jpg, This was the only RML heavy gun not to be issued with gas-checks.

Surviving examples

* Restore
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
Several 6½ ton Mk I guns on Ascension Island
* 6½ ton Mk I at

Fort Siloso Fort Siloso is a decommissioned coastal artillery battery in Sentosa, Singapore. It consists of 12 such batteries which made up "Fortress Singapore" at the start of World War II, and saw action during the Battle of Singapore. The fort is now a ...

, Singapore
6½ ton Mk III of 1869, at Elizabeth Castle, Jersey, UK
* Remains of several 7 ton Mk III guns on

Flat Holm Flat Holm () is a Welsh island lying in the Bristol Channel approximately from Lavernock Point in the Vale of Glamorgan. It includes the most southerly point of Wales. The island has a long history of occupation, dating at least from the B ...

island, UK * Nine 7 ton Mk III guns on

Steep Holm Steep Holm ( and later ) is an English island lying in the Bristol Channel. The island covers at high tide, expanding to at mean low water. At its highest point it is above mean sea level. Administratively it forms part of the unitary autho ...

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) Signal Hill (Afrikaans: ''Seinheuwel''), or Lion's Rump, is a landmark flat-topped hill located in Cape Town, next to Lion's Head and Table Mountain. The hill was also known as "The Lion's Flank", a term now obsolete. Together with Lion's He ...

, South Africa.

Notes and references

Bibliography

Treatise on the construction and manufacture of ordnance in the British service. War Office, UK, 1877

Treatise on Ammunition. War Office, UK, 1877

* Sir Thomas Brassey
The British Navy, Volume II. London: Longmans, Green and Co. 1882

Text Book of Gunnery, 1887. LONDON : PRINTED FOR HIS MAJESTY'S STATIONERY OFFICE, BY HARRISON AND SONS, ST. MARTIN'S LANE

Brassey's Naval Annual, 1888
*

External links

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

{{DEFAULTSORT:RML 07-inch gun Artillery of the United Kingdom Naval guns of the United Kingdom 178 mm artillery Victorian-era weapons of the United Kingdom Coastal artillery 175 mm artillery