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BL 4.7 inch (120 mm) 45 calibre naval gun
HMAS Stuart A 4.7 inch gun.jpg
"A" gun on destroyer HMAS Stuart, circa. 1930s
Type Naval gun
Service history
In service 1918–45
Used by  United Kingdom
Wars World War I World War II
Production history
Designed 1917
Variants Mk I, Mk II[1]
Barrel length 5.4 metres (213 in) bore (45 calibres)

Shell 50 pounds (22.68 kg)[2]
Calibre 120 millimetres (4.724 in)
Muzzle velocity 814 metres per second (2,670 ft/s)[3]
Maximum range 14,450 metres (15,800 yd)[4]

The BL 4.7 inch 45 calibres gun (actually a metric 120 mm gun) was a British medium-velocity naval gun introduced in 1918 for destroyers, to counter a new generation of heavily-armed destroyers Germany was believed to be developing.

Description and History

Gunners on destroyer HMS Broke (D83), September 1940

Mk I, of built-up wire-wound construction, went into service beginning in 1918 on destroyers of the new Admiralty type destroyer leader (Scott class) and Thornycroft type leader (Shakespeare class). Some saw service in World War I, but most entered service after the war ended.

It was also mounted on :

Mk II was a monobloc-barrel (i.e. single-piece, typical of small-medium World War II guns) gun of similar performance introduced in World War II to replace the worn-out Mk I guns on surviving ships.

These were the only BL-type 4.7 inch guns in British service, all others have been of the QF-type. They were superseded on new destroyers from 1930 by the 4.7 inch QF Mark IX.


See also

Weapons of comparable role, performance and era


  1. Mk I = Mark 1, Mk II = Mark 2. Britain used Roman numerals to denote Marks (models) of ordnance until after World War II, and used separate number series for BL and QF guns of the same calibre. Hence these were the first (and only) two models of British BL 4.7-inch guns.
  2. DiGiulian
  3. Mk I : 814 m/s :
  4. Mk I : 14450 metres :


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