BL 4.7 inch /45 naval gun

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, intended to counter a new generation of heavily armed destroyers that Germany was believed to be developing.

Country Name Origin Year
United Kingdom - UK (Great Britain) 1918
Country Name Operational Year Retirement Year
United Kingdom - UK (Great Britain) 1918 1945 View

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 :

  • Faulknor class destroyer leaders as re-gunned in 1918
  • Thornycroft and Admiralty Modified W Class destroyers completed 1919 – 1920
  • Prototype destroyers HMS Ambuscade and HMS Amazon commissioned 1926 & 1927

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 They were superseded on new destroyers from 1930 by the 4.7 inch QF Mark IX.

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
Barrel length 5.4 metres (213 in) bore (45calibres)
Shell 50 pounds (22.68 kg)
Calibre 120 millimetres (4.724 in)
Muzzle velocity 814 metres per second (2,670 ft/s)
Maximum firing range 14,450 metres (15,800 yd)

End notes