BL 4-inch Mk VIII naval gun

The BL 4-inch Mark VIII naval gun^{[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.^[2]

Ordnance BL-4-inch Mk VIII naval gun
Forward gun of HMS Defender
Type	Naval gun
Service history
In service	1908–1945
Used by	United Kingdom Australia
Wars	World War I – World War II
Production history
Designed	1904[1]
No. built	Mk VIII: 246 Mk XI: 30[1]
Variants	Mk VIII – Mk XI[1]
Specifications
Mass	2,912 pounds (1,320 kg) (barrel & breech)[2]
Barrel length	159.2 inches (4.044 m) bore (40 calibres)[2]
Shell	31 pounds (14.06 kg) Common pointed, Common lyddite[2]
Calibre	4 inches (101.6 mm)
Breech	Welin, single-motion screw[2]
Elevation	-10° to +20°[1]
Rate of fire	6-8 RPM[1]
Muzzle velocity	2,287 feet per second (697 m/s)[3]
Maximum firing range	10,210 yards (9,340 m)[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 :

• HMS Swift laid down 1905
• Tribal-class destroyers from HMS Saracen (1908) onwards.
• Beagle-class destroyer of 1909
• Acorn-class destroyers of 1910
• Acheron-class destroyers of 1910
• River-class torpedo-boat destroyers (Australia) of 1910.

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 Mark XI-variant was adapted to arm the K-class submarines laid down 1915.

See also

• List of naval guns
• German 10.5 cm SK L/40 naval gun – firing slightly heavier shell

Notes

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.