RML 12.5 inch 38 ton gun

Ordnance RML 12.5 inch 38 ton gun
Gun at Fort Nelson, Portsmouth, UK
Type	Naval gun Coast defence gun
Place of origin	United Kingdom
Service history
In service	1875 - 190?
Used by	Royal Navy
Production history
Designer	Royal Gun Factory
Designed	1874
Manufacturer	Royal Arsenal
Variants	Mk I, Mk II
Specifications
Barrel length	198 inches (5.0 m) (bore)^[1]

Shell	800 to 809 pounds (362.9 to 367.0 kg) Palliser, Common, Shrapnel
Calibre	12.5-inch (317.5 mm)
Muzzle velocity	Mk I : 1,425 feet per second (434 m/s)^[2] Mk II : 1,575 feet per second (480 m/s)^[3]
Maximum firing range	Mk I : 6,000 yards (5,500 m) Mk II : 6,500 yards (5,900 m)

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

Design

Mark I gun barrel construction

The gun originated from a desire for a longer 12-inch gun than the existing RML 12 inch 35 ton gun. 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 "A" tube toughened in oil, surrounded by wrought iron "B" tube, triple coil in front of the trunnion, coiled breech-piece and breech coil. This was approved in January 1875.^[4]

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.

RML 12.5in Studded Shell, located at Hurst Castle, 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.^[5] 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.

Surviving examples

At Hurst Castle, UK
At Fort Nelson, Portsmouth, UK
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, Malta

Notes and references

↑ Treatise on Construction of Service Ordnance 1877, page 292
↑ 1,425 feet/second firing 800-pound projectile with "Battering charge" of 130 pounds "P2" (gunpowder). Treatise on Construction of Service Ordnance 1877, page 347.
↑ Muzzle velocity of 1,575 feet/second firing an 809lb 6oz projectile with a charge of 210 pounds Prism2 black powder, is quoted for Mark II gun in "Text Book of Gunnery 1887" Table XVI.
↑ Treatise on Construction of Service Ordnance 1877, pages 286-287
↑ Handbook for RML 12.5 inch gun (1885) pp. 32-33; Plates XI-XIV

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
[http://handle.slv.vic.gov.au/10381/103338Sectretary of State for War (1885). Handbook for the R.M.L. 12.5-inch 38-ton Gun, Marks I and II. London: Her Majesty's Stationery Office. ]

External links

Wikimedia Commons has media related to RML 12.5 inch 38 ton naval gun.

Diagram of gun on small port 6 foot recoil carriage at Victorian Forts and Artillery website
Diagram of gun on Casemate Platform, 6 feet recoil Mark III at Victorian Forts and Artillery website
Diagram of gun on on Dwarf 'C' Pivot Mark III at Victorian Forts and Artillery website

British Empire naval weapons of the Victorian era

Smoothbore muzzle-loading cannons	18-pounder 24-pounder 32-pounder 58 cwt 68-pounder Somerset cannon

Smoothbore muzzle-loading shell guns	8 inch 10-inch 86 cwt

Mortars	10-inch Blomefield 13-inch Blomefield

Howitzers	12-pounder Millar 24-pounder Millar

Rifled breechloaders (Armstrong)	RBL 9 pounder RBL 20 pounder RBL 40 pounder RBL 7 inch 110 pounder

Rifled muzzle-loaders (Lancaster)	68-Pounder Lancaster gun

Rifled muzzle-loaders (converted)	RML 64 pounder 71 cwt

Rifled muzzle-loaders (Woolwich)	RML 9 pounder 8 cwt RML 64 pounder 64 cwt RML 7 inch RML 8 inch RML 9 inch RML 10 inch RML 11 inch RML 12 inch 25 ton RML 12 inch 35 ton RML 12.5 inch RML 16 inch

Quick-firing guns	QF 3-pounder Hotchkiss QF 6-pounder Hotchkiss QF 6 pounder Nordenfelt QF 12-pounder 12 cwt Mk I QF 4 inch QF 4.7 inch QF 6 inch

Breech-loaders (new pattern)	BL 4 inch BL 5 inch BL 6 inch 80 pounder BL 6 inch Mk II – VI BL 8 inch BL 9.2 inch Mk I – VII BL 9.2 inch Mk VIII BL 10 inch BL 12 inch Mk I – VII BL 12 inch Mk VIII BL 13.5 inch BL 16.25 inch

Light weapons	Gatling gun Gardner gun Nordenfelt gun 1-inch Nordenfelt gun

Torpedoes	Whitehead torpedo

British Empire Small Arms & Ordnance of the Victorian era

Side arms

Muskets and Rifles

Artillery

Field Artillery	SBML 9 pounder 13 cwt RBL 9 pounder RBL 12 pounder RBL 20 pounder RML 9 pounder 8 cwt RML 13 pounder 8 cwt RML 16 pounder 12 cwt BL 12 pounder 7 cwt BL 12 pounder 6 cwt QF 12 pounder 8 cwt BL 15 pounder QF 1 pounder pom-pom

Mountain artillery	RML 7 pounder Mountain Gun RML 2.5 inch Mountain Gun

Howitzers, medium, and heavy artillery	RML 6.3 inch Howitzer RML 6.6 inch howitzer BL 5 inch Howitzer BL 5.4 inch Howitzer

Siege & garrison artillery	SBBL 32 pounder SBML 24 pounder SBML 8 inch 65 cwt RBL 40 pounder RBL 7 inch RML 25 pounder 18 cwt RML 40 pounder gun RML 64 pounder 64 cwt gun RML 64 pounder 58 cwt RML 64 pounder 71 cwt gun RML 80 pounder RML 6.6 inch gun RML 8 inch howitzer BL 5 inch gun Mk I - V BL 6 inch 30 cwt howitzer BL 9.45-inch howitzer

Coastal artillery	QF 4.7 inch BL 6 inch Mk III, IV, VI BL 6 inch Mk V RBL 7 inch RML 7 inch RML 8 inch BL 8 inch Mk VII RML 9 inch BL 9.2 inch Mk IV & VI BL 10 inch Mk I BL 12 inch Mk I, VI, VII RML 12.5 inch RML 16 inch RML 17.72 inch

Mortars

13 inch 36 cwt mortar
10 inch 18 cwt mortar
8 inch 9 cwt mortar

War rockets

Congreve 6-pounder
Congreve 12-pounder
Congreve 24-pounder
Boxer
Hales 9-pounder
Hales 24-pounder

Machine guns

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