RML 12.5 inch 38 ton gun
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The RML 12.5-inch guns were large rifled muzzle-loading guns designed for British battleships and were also employed for coast defence.


Design

The gun originated from a desire for a longer 12-inch gun than the existing
RML 12-inch 35-ton gun RML 12-inch 35-ton guns were large rifled muzzle-loading guns used as primary armament on British battleships of the 1870s. They were the longer and more powerful of the two 12-inch British RML guns, the other being the 25-ton gun. Design T ...
. Experiments in 1874 with both 12-inch and 12.5-inch versions 3 feet longer than the existing 12-inch gun showed the 12.5-inch calibre was more suitable, and further experiments showed a projectile of 800 pounds could be fired with a charge of 130 pounds of P2 gunpowder without undue strain. The same construction as in the existing 12-inch 35-ton gun was used : a
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 ...
"A" tube toughened in oil, surrounded by
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 ...
"B" tube, triple coil in front of the trunnion, coiled breech-piece and breech coil. This was approved in January 1875. The gun was rifled on the "Woolwich" pattern of a small number of broad shallow rounded grooves, with 9 grooves increasing from 0 to 1 turn in 35 calibres ( i.e. 1 turn in 437.5 inches). Mark II had an enlarged powder chamber and attained higher muzzle velocity and slightly longer range. This gun was the final development of large British rifled muzzle-loading guns before it switched to breechloaders beginning in 1880. It was succeeded in its class on new battleships by the BL 12-inch Mk II gun.


Naval service

Guns were mounted on HMS ''Dreadnought'' commissioned in 1879, HMS ''Agamemnon'' commissioned in 1883, and HMS ''Ajax'' commissioned in 1885, the last British warships completed with muzzle-loading guns.


Ammunition

When the gun was first introduced projectiles had several rows of "studs" which engaged with the gun's rifling to impart spin. Sometime 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. 38 ton gun shell - Hurst Castle.jpg, 1 RML 12.5-inch Mk I shrapnel shell diagram.jpg, 2 RML 12.5in Studded Palliser Shell Mk III with Attached Gas-Check Mk II.JPG, 3 RML 12.5in Studded Common Shell with Attached Gas-Check Mk II.JPG, 4 RML 12.5in Studded Shrapnel Shell with Attached Gas-check Mk II.JPG, 5 RML 12.5in Case Shot Mk III.JPG, 6 RML 12.5in Studless Palliser Shell Mk I with Automatic Gas-Check.JPG, 7 RML 12.5in Studless Common Shell Mk I with Automatic Gas-Check.JPG, 8 RML 12.5-inch Studless Shrapnel Shell.jpg, 9 # RML 12.5in Studded Shell, located at
Hurst Castle Hurst Castle is an artillery fort established by Henry VIII on the Hurst Spit in Hampshire, England, between 1541 and 1544. It formed part of the king's Device Forts coastal protection programme against invasion from France and the Holy Roman ...
, UK # RML 12.5in Studded Shrapnel Shell Mk I with Attached Gas-Check Mk I # RML 12.5in Studded Palliser Shell Mk III with Attached Gas-Check Mk II # RML 12.5in Studded Common Shell Mk I with Attached Gas-Check Mk II # RML 12.5in Studded Shrapnel Shell Mk I with Attached Gas-check Mk II # RML 12.5in Case Shot Mk III # RML 12.5in Studless Palliser Shell Mk I with Automatic Gas-Check # RML 12.5in Studless Common Shell Mk I with Automatic Gas-Check # RML 12.5in Studless Shrapnel Shell Mk I with Automatic Gas-check Images 3–9 show the range of ammunition for the RML 12.5-inch gun in 1885.Handbook for RML 12.5-inch gun (1885) pp. 32-33; Plates XI-XIV By this time the gun no longer fired studded ammunition without gas-checks. Instead there were two sets of ammunition available, namely: older studded ammunition with attached gas-checks Mk II, and newer studless ammunition with automatic gas-checks. Case ammunition neither was studded nor required gas-checks. Also by this time, attached gas-checks Mk I as shown in image 2 had been superseded by attached gas-checks Mk II.


See also

*
List of naval guns List of Naval Guns by country of origin in decreasing caliber size List of naval guns by caliber size, all countries Naval anti-aircraft guns See also *List of artillery *List of the largest cannon by caliber *Glossary of British ordnance ...


Surviving examples

* Two at
Hurst Castle Hurst Castle is an artillery fort established by Henry VIII on the Hurst Spit in Hampshire, England, between 1541 and 1544. It formed part of the king's Device Forts coastal protection programme against invasion from France and the Holy Roman ...
, UK, originally at Cliff End Battery * At
Fort Nelson, Portsmouth Fort Nelson, in the civil parish of Boarhunt in the English county of Hampshire, is one of five defensive forts built on the summit of Portsdown Hill in the 1860s, overlooking the important naval base of Portsmouth. It is now part of the Royal A ...
, UK, originally at Cliff End Battery
Outside Fort Albert, Isle of Wight

No 22 of 1876 outside Calbourne Mill, Isle of Wight, originally at Cliff End Battery

An unpreserved gun
at
Fort Delimara Fort Delimara ( mt, Il-Fortizza ta' Delimara) is a polygonal fort in Marsaxlokk, Malta. It was built between 1876 and 1888 by the British as part of a chain of fortifications intended to protect Marsaxlokk Harbour. Today, the fort is still intact ...
, Malta
Gun on replica carriage
at
Harding's Battery Harding's Battery is a restored artillery battery in the British Overseas Territory of Gibraltar. It is located at Europa Point and includes the Europa Sunken Magazine that is now used as a visitor centre. History This battery is on Europa Point ...
, Gibraltar
Gun number 87 and 95, dated 1878. Now in the ditch
at Fort Cunningham, Bermuda


Notes and references


Bibliography


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



External links


Handbook for the R.M.L. 12.5-inch 38-ton gun, marks I and II : casemate, dwarf, and small port mountings (land service). Great Britain. War Office. London : H.M.S.O. 1885
at State Library of Victoria
Handbook for the 12.5-inch 38-ton R.M.L. gun, marks I and II, casemate, dwarf, and small part mountings land service 1888, 1893, 1899, 1904
at State Library of Victoria

at Victorian Forts and Artillery website

at Victorian Forts and Artillery website

at Victorian Forts and Artillery website {{VictorianEraBritishWeapons Naval guns of the United Kingdom 320 mm artillery Victorian-era weapons of the United Kingdom Coastal artillery