The QF 4 inch Mk XVI gun was the standard British Commonwealth naval anti-aircraft and dual-purpose gun of World War II.

Service

The Mk XVI superseded the earlier QF 4 inch Mk V naval gun on many Royal Navy ships during the late 1930s and early 1940s. The ammunition fired by the Mk V gun and the Mk XVI guns were different. The ammunition for the Mk V gun was 44.3 in long and weighed 56 lb, while the ammunition fired by the Mk XVI gun was 42.1 in long and weighed 66.75 lb. The weight of the high-explosive projectile grew from 31 lb for the Mk V to 35 lb for the Mk XVI. There were three variants of the gun produced with differing construction methods. The original Mk XVI had an A tube, jacket to 63.5 in from the muzzle and a removable breech ring. The Mk XVI* replaced the A tube with an autofretted loose barrel with a sealing collar at the front of the jacket. The Mk XXI was a lighter version with an autofretted monobloc barrel and a removable breech ring. The total number of Mk XVI and XVI* guns produced was 2,555, while there were 238 Mk XXI guns produced. Of those totals ,604 Mk XVI* and 135 of the Mk XXI guns were produced in Canada and 45 of the Mk XVI* were produced in Australia. These guns were usually mounted on HA/LA Mark XIX twin mountings, although several Australian frigates and corvettes had single-gun Mk XX mountings. The last Royal Navy ship to operate with a Mark XIX twin mounting was HMS Mermaid (F76), which had originally been designed for the Ghana Navy and so required a simple and inexpensive main armament. Acquired by the British Government in 1972, she served until 1977 when she was purchased by the Royal Malaysian Navy and renamed KD Hang Tuah.

List of equipped vessels

As secondary armament

(list not complete)

As main armament

(list not complete)

Allied ships fitted out in Britain

Post-war construction ships

The South African Navy Loch-class frigates (HMSAS Good Hope and HMSAS Transvaal) each had two of these guns mounted on a twin Mark XIX mount on their foredeck between 1955 and 1976.

Ammunition

Surviving examples