BL 5 inch gun Mk I – V

Ordnance BL 5 inch gun Mks I - V

Mk I coast defence gun outside entrance to the Hong Kong Museum of Coastal Defence
Type Naval gun
Coast defence gun
Field gun
Service history
In service 1880 - 1918
Used by  United Kingdom
Wars Second Boer War
Production history
Variants Mks I - V
Weight Mk I - II  : 38 long hundredweight (1,930 kg)
Mk III - V : 40 long hundredweight (2,030 kg)
Barrel length 125 inches (3,175 mm) bore (25 calibres)[1]

Shell 50 pounds (22.68 kg)[1]
Calibre 5-inch (127.0 mm)
Breech de Bange
Muzzle velocity 1,750 feet per second (533 m/s)[2]
Maximum firing range 8,700 yards (8,000 m)[1]

The BL 5 inch guns Mk I - Mk V[note 1] were early British 5-inch rifled breechloading naval guns after it switched from rifled muzzle-loaders in the late 1870s. They were originally designed to use the old gunpowder propellants. The 5-inch calibre was soon discontinued in favour of QF 4.7-inch.

Naval service

Working a starboard broadside gun on Vavasseur recoil mounting on HMS Calliope

Guns equipped the following British warships :

These guns also equipped several small gunboats of Colonial navies of Australia in the 1880s in response to the perceived threat of Russian expansionism in the Pacific (The "Russian scares").

Second Boer War (1899 - 1902) field gun

In South Africa, circa. 1900

A number of guns mounted on carriages from obsolete RML 40 pounder guns accompanied the British siege train (heavy artillery) to South Africa. They were not required for the expected siege of Pretoria, which did not eventuate. Its usefulness in the field was limited by lack of a recoil control system, and the QF 4.7 inch gun was the most commonly used British heavy gun in the war.[5]

Coast defence gun

The gun was installed as a conventional coast defence gun in South Africa and Australia, and several in the United Kingdom. Its more common use ashore in the UK was as "moveable armaments" in forts : on 2-wheeled carriages similar to field carriages but intended only for moving short distances to position guns for defence of the fort. These used either obsolete 40-pounder RML carriages or special high-mounting carriages for firing over parapets with recoil controlled by a hydraulic buffer built into the platform to which the carriage was fastened.[6]


See also

Surviving examples

One of two guns outside the Union Buildings, Pretoria, South Africa


  1. Mk I - Mk V = Marks 1 through to 5. Britain used Roman numerals to denote Marks (models) of ordnance until after World War II. Hence this article covers the five models of BL 5-inch naval guns.


  1. 1 2 3 Text Book of Gunnery 1902, Table XII page 336
  2. Firing a 50-pound projectile with 15½ lb S.P. (gunpowder) or 4 lb 7¼ oz cordite Mk I propellant. Text Book of Gunnery 1902.
  3. Winfield (2004). p.293
  4. Preston (2007) p.182
  5. Hall, June 1972
  6. Hogg & Thurston 1972, pages 114-115


External links

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