QF 4 inch naval gun Mk I – III

Ordnance QF 4-inch gun Mk I, II, III
Australian troops with gun on a transport ship, circa. November 1914
Type	Naval gun Coast defence gun
Place of origin	United Kingdom
Service history
In service	1896 - 1920
Used by	British Empire
Wars	Boxer Rebellion, World War I
Production history
Designed	1895
Specifications
Weight	2,912 pounds (1,321 kg) barrel & breech
Barrel length	160 inches (4.064 m) bore (40 cal); 165.35 inches (4.200 m) total
Shell	Separate-loading QF 25 pounds (11.34 kg) Common pointed or Lyddite
Calibre	4-inch (101.6 mm)
Breech	Single-motion screw
Muzzle velocity	2,300 feet per second (700 m/s)
Maximum firing range	9,000 yards (8,200 m)

The QF 4-inch gun Mks I, II, III were early British QF (quick-firing) naval guns originating in 1895. They all had barrels of 40 calibres length.

The gun was intended to be a more powerful alternative to the quick-firing 3-inch QF 12-pounder gun, and a faster-firing replacement for the BL 4-inch gun.

It was mounted on the following ships :

Its 25-pound (11 kg) shell proved insufficiently powerful to make it much of an improvement on the 12-pounder. From 1907 onwards it was succeeded in its class on new warships by the BL 4 inch gun Mk VIII, which fired a 31-pound (14 kg) shell.

From 1906 a number of Mk III guns were transferred from the Royal Navy for use as coast defence guns around the United Kingdom, and remained until 1939.

In 1918 three guns were in service at Dover Garrison and eight at Forth Garrison.

On 20 September 1914 the British cruiser HMS Pegasus was sunk by SMS Königsberg in Zanzibar harbour. Her 8 QF 4-inch Mk III guns were recovered and used ashore in the East African campaign. Some were used as coast defence guns at Zanzibar and Mombasa. Two guns, and from 11 February 1916, three guns, were used by 10th Heavy Battery manned by the Royal Marines, mounted on improvised field carriages and towed by Packard lorries, supported by six REO lorries carrying ammunition.