The QF 4-inch gun Mk IV[note 1] was the main gun on most Royal Navy and British Empiredestroyers 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.[1] 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.
British sailors loading a QF 4 inch Mk IV gun in 1942
Diagram of a QF 4 inch Mk IV gun cartridge.
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fired a heavier 35 pounds (16 kg) projectile from late 1944.[2] Shortly after the end of hostilities, the Mk XXII was superseded in new British submarines by the lighter QF 4 inch Mk XXIII.[4]
^Mk IV = Mark 4. Britain used Roman numerals to denote Marks (models) of ordnance until after World War II. This was the fourth model of 4-inch QF naval gun. Variants Mk XII = Mark 12, Mk XXII = Mark 22.
^2,370 ft/s for Mk IV gun with 31 lb (14 kg) projectile in WWI, using 5 lb 1 oz 12 drams cordite MD size 16 propellant (Treatise on Ammunition, 10th Edition 1915)