The RML 12-inch 25-ton guns were large rifled muzzle-loading guns of mid-late 1800s used as primary armament on British ironclad turret battleships and coastal monitors, and also ashore for coast defence. They were the shorter and less powerful of the two 12-inch (305-mm) British RML guns, the other being the 35-ton gun.

Design

HMS Hotspur (1870) 12-inch gun rear view

Mark I

Four guns were first made in 1866 with a toughened

mild steel Carbon steel is a steel with carbon content from about 0.05 up to 2.1 percent by weight. The definition of carbon steel from the American Iron and Steel Institute (AISI) states: * no minimum content is specified or required for chromium, cobalt ...

tube surrounded by multiple

wrought iron Wrought iron is an iron alloy with a very low carbon content (less than 0.08%) in contrast to that of cast iron (2.1% to 4%). It is a semi-fused mass of iron with fibrous slag Inclusion (mineral), inclusions (up to 2% by weight), which give it a ...

coils on the original Armstrong pattern.

Mark II

While strong, the multiple coils were considered too expensive for construction in quantity. From 1867 guns were built on the simplified and hence cheaper "Fraser" system involving fewer but larger coils similar to the 10-inch (254-mm) Mk II gun. The guns were not considered a success, with the rifling twist of 1 in 100 increasing to 1 in 50 considered insufficient for accuracy, and guns were retubed in 11-inch (279-mm) calibre when their bores wore out.Treatise on Construction of Service Ordnance 1877, pages 92-94

Naval service

Guns were mounted on : * : 4 * : 4 * : 2 * : 2 * : 4 * : 4

Ammunition

When the gun was first introduced projectiles had several rows of "studs" which engaged with the gun's rifling to impart spin. Some time after 1878, " attached gas-checks" were fitted to the bases of the studded shells, reducing wear on the guns and improving their range and accuracy. Subsequently, " automatic gas-checks" were developed which could rotate shells, allowing the deployment of a new range of studless ammunition. Thus, any particular gun potentially operated with a mix of studded and studless ammunition. The gun's primary projectile was 600 to 608-pound (272- to 275-kilogram) " Palliser" armour-piercing shot, fired with a "Battering charge" of 85 pounds (38.5 kilograms) of "P" (gunpowder) or 67 pounds (30.4 kilograms) "R.L.G." (gunpowder) for maximum velocity and hence penetrating power.

Shrapnel Shrapnel may refer to: Military * Shrapnel shell, explosive artillery munitions, generally for anti-personnel use * Shrapnel (fragment), a hard loose material Popular culture * ''Shrapnel'' (Radical Comics) * ''Shrapnel'', a game by Adam C ...

and

Common Common may refer to: Places * Common, a townland in County Tyrone, Northern Ireland * Boston Common, a central public park in Boston, Massachusetts * Cambridge Common, common land area in Cambridge, Massachusetts * Clapham Common, originally com ...

(exploding) shells weighed 497 pounds (225.5 kilograms) and were fired with a "Full charge" of 55 pounds (25 kilograms) "P" or 50 pounds (22.7 kilograms) "R.L.G.".Treatise on Ammunition 1877, pages 191,194, 220 RML 12-inch 25-ton Palliser shot diagram.jpg,

Surviving examples

at Drake's Island, Plymouth, UK

Notes and references

Bibliography

Treatise on Ammunition. War Office, UK, 1877

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

Text Book of Gunnery, 1887. LONDON : PRINTED FOR HIS MAJESTY'S STATIONERY OFFICE, BY HARRISON AND SONS, ST. MARTIN'S LANE
* Sir Thomas Brassey
The British Navy, Volume II. London: Longmans, Green and Co. 1882

External links

{{VictorianEraBritishNavalWeapons Naval guns of the United Kingdom 305 mm artillery Victorian-era weapons of the United Kingdom Coastal artillery