BL 4 inch naval gun Mk VIII

Ordnance BL 4 inch gun Mk VIII

Forward gun of HMS Defender
Type Naval gun
Service history
In service 1908 - 1945
Used by  United Kingdom
Weight 2,912 pounds (1,320 kg) (barrel & breech)[1]
Barrel length 159.2 inches (4.044 m) bore (40 calibres)[1]

Shell 31 pounds (14.06 kg) Common pointed, Common lyddite[1]
Calibre 4 inches (101.6 mm)
Breech Welin, single-motion screw[1]
Muzzle velocity 2,287 feet per second (697 m/s)[2]
Maximum firing range 10,210 yards (9,340 m)[3]

The BL 4-inch gun Mark VIII[note 1] was a British medium-velocity wire-wound naval gun introduced in 1908 as an anti-torpedo boat gun in smaller ships whose decks could not support the strain of the heavier and more powerful Mk VII gun.[1]

Mk VIII History

Breech of gun on HMAS Huon in March 1919

The gun succeeded the QF 4 inch Mk III, whose 25-pound (11 kg) shell had been considered insufficiently powerful for its intended role. The BL Mk VIII fired a 31-pound (14 kg) shell. It armed the following warships :

The gun was succeeded in its class from 1911 by the QF 4 inch Mk IV.

In World War II many guns were used to arm merchant ships.

Mk XI submarine gun

A Mk XI variant was adapted to arm submarines :

See also


  1. Mark VIII = Mark 8. Mark XI = Mark 11. Britain used Roman numerals to denote marks (models) of ordnance until after World War II. This was the eighth model of British BL 4-inch gun.


  1. 1 2 3 4 5 HANDBOOK for the 4" Mark VII. and VIII. B.L. Guns 1913
  2. 2287 ft/second firing a 31 lb 3 C.R.H. projectile, using 5 lb 4 oz cordite MD size 16 propellant. HANDBOOK for the 4" Mark VII. and VIII. B.L. Guns 1913.
  3. DiGiulian


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