QF 4-inch naval gun Mk IV, XII, XXII

The QF 4-inch gun Mk IV was the main gun on most Royal Navy and British Empire destroyers in World War I. It was introduced in 1911 as a faster-loading light gun successor to the BL 4 inch Mk VIII gun. Of the 1,141 produced, 939 were still available in 1939. Mk XII and Mk XXII variants armed many British interwar and World War II submarines.

Mk IV gun


Mk IV armed many British destroyers and some cruisers in World War I. It was used to arm merchant ships in World War II.

The guns armed the following warships :
 * Forward-class scout cruisers as re-gunned in 1911
 * Sentinel-class scout cruisers as re-gunned 1911-1912
 * Pathfinder-class scout cruisers as re-gunned 1911-1912
 * Adventure-class scout cruisers as re-gunned 1911-1912
 * Acasta (K)-class destroyers of 1911
 * Laforey (L)-class destroyers of 1913
 * Yarrow M-class destroyers laid down 1912 - 1915
 * Admiralty M-class destroyer of 1913
 * Thornycroft M-class destroyers laid down 1913 - 1915
 * Hawthorn M-class destroyer of 1914
 * Talisman-class destroyers of 1914
 * Medea-class destroyers of 1914
 * Faulknor-class leaders of 1914
 * Marksman-class destroyers of 1914
 * Parker class leaders of 1915
 * Yarrow Later M-class destroyers of 1915
 * R-class destroyers of 1916
 * S-class destroyers of 1917
 * Fundy-class minesweepers of 1938 (guns from decommissioned Canadian S-class destroyers)

Mk XII and XXII submarine gun


The Mk XII variant was developed for arming submarines from 1918, Mk XXII was developed to arm submarines during World War II. These submarine guns fired a heavier 35 lb projectile from late 1944. Shortly after the end of hostilities, the Mk XXII was superseded in new British submarines by the lighter QF 4 inch Mk XXIII.

Mk XII and XXII equipped submarines

 * L class
 * Odin ("O") class
 * Parthian ("P") class
 * River (or Thames) class
 * Grampus (or Porpoise) class
 * Triton ("T") class
 * S class
 * Some of the Amphion ("A" or Acheron) class

Surviving guns

 * The Mk IV gun from HMS Lance (1914) which fired the first British shot of World War I on 5 August 1914 is on display at the National Museum of the Royal Navy, Portsmouth (on loan from the Imperial War Museum).
 * A Mk IV gun on a 1945 Mk XVI mounting is on display at the Heugh Gun Battery Museum in Hartlepool, County Durham.
 * A Mk IV gun on a pedestal mounting is still in situ at Ordnance Point in the Falkland Islands, where it is believed to have been installed in 1943.
 * A First World War 4-inch naval gun, tentatively identified as a Mk IV, stands outside the Army, Navy and Air Force Veterans Hall in 4th Street, Sidney, British Columbia.

Weapons of comparable role, performance and era

 * 10.5 cm SK L/45 naval gun : German WWI equivalent
 * 10.5 cm SK C/32 naval gun : Slightly more powerful German equivalent WWII submarine gun
 * 4"/50 caliber gun : US Navy equivalent