QF 12-pounder 18 cwt naval gun

The QF 12 pounder 18 cwt gun was a 3-inch high-velocity naval gun used to equip larger British warships such as battleships for defence against torpedo boats. 18 cwt referred to the weight of gun and breech (18 × 112 lb = 2,016 lb or 914 kg), to differentiate the gun from others that also fired the "12 pound" (actually 12.5 lb or 5.7 kg) shell.

Ordnance QF 12-pounder 18 cwt
Deployed as anti-aircraft gun on HMS Agamemnon off Salonika, 1916
TypeNaval gun, Coastal defence
Place of originUnited Kingdom
Service history
In service1906–1921?
Used byRoyal Navy
WarsWorld War I
Production history
DesignerElswick Ordnance Company
MassGun & breech: 2,016 lb (914 kg)
Barrel lengthBore: 150-inch (3.81 m) (50 calibres)

ShellSeparate QF 12.5 lb (5.66 kg)
Calibre3 in (76 mm)
Rate of fire20 rd/min[1]
Muzzle velocity2,600 ft/s (790 m/s)[2]
Effective firing range9,300 yards @ +20°
(8,500 m @ +20°)


Royal Navy service

Guns were mounted in:[3]

The gun was superseded in the anti-torpedo boat role on new capital ships from 1909 onwards by the far more powerful BL 4-inch Mk VII gun.

World War I land service

In World War I four guns were landed for service in the East Africa campaign, on 10 February 1916, and were used until September. They constituted the 9th Field Battery manned by Royal Marines. They were originally towed by oxen and later by Napier lorries.[4]

Fourteen of these guns were mounted in coast defence batteries in the 'Middle Line' of the defences of the Firth of Forth when it was established in 1915 (the batteries on Inchcolm (8 guns), Inchmickery (4) and Cramond Island (2). During the general revision of the defences in 1916/17 two of the guns were removed to store, four moved to other batteries (Hound Point and Downing Point). The document setting out the armaments of the Forth differentiate clearly between the 12cwt and 18cwt types, both of which were in use in the fortress.[5]


The gun fired the same 12.5 lb 3-inch (76 mm) shells as the other British "QF 12 pounder" guns, but used its own larger separate cartridge case to accommodate a larger quantity of cordite propellant.

2 lb 12 oz (1.25 kg) cordite Cartridge Mk II, 1914
Mk II common pointed shell
Mk II & Mk III Common Lyddite shell
Mk IV Common Lyddite shell with internal night tracer, 1914
Mk IX Shrapnel shell, 1918

See also


  1. 20 rounds per minute is quoted in Elswick gun tables of 1901, and may be considered optimistic
  2. 2600 ft/s: Range Tables for His Majesty's Fleet, 1910 February 1911 with 2 lb 12 oz (1.25 kg) cordite MD propellant. The gun first appears in Elswick gun Tables as quoted in Brasseys Naval Annual 1901 with a maximum muzzle velocity 2800 ft/s with "battering" charge of 3 lb cordite (Mk I), but this is not the charge adopted for British service.
  3. The Sight Manual 1916
  4. Farndale 1988, pages 316, 391. Farndale, quoting from the Official History, states they were from HMS Pegasus, but it did not carry these guns.
  5. 'History of Forth Defences from 1914 to November 1918' Fort Record Book, Inchcolm Fire Command, The National Archives, Kew, reference WO 192/108.


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