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
Mk IV gun from HMS Lance at Imperial War Museum Naval Gallery in South Kensington, London 1926
On R-class destroyer HMS Satyr c. 1917–1918
Gun recoiling after firing, on Australian auxiliary anti-submarine vessel HMAS Wilcannia c. 1943
Rusted QF 4 inch mk IV gun without a gun shield on East Falkland
4-inch/50-caliber gun
Videos
The 4″/50-caliber gun was the standard low-angle, quick-firing gun for the United States, first appearing on the monitor Arkansas and then used on "Flush Deck" destroyers through World War I and the 1
QF 4-inch naval gun Mk IV, XII, XXII
…10.5 cm SK C/32 naval gun : Slightly more powerful German equivalent WWII submarine gun 4"/50 caliber gun : US Navy equivalent Tony DiGiulian, British 4"/40 (10.2 cm) QF Marks IV, XII and XXII…
The gun from USS Ward which fired the first American shot of World War II at Pearl Harbor on 7 December 1941 at the State Capitol grounds in St. Paul, Minnesota.
4-inch/50-caliber gun on merchant ship SS Sommelsdijk