The original Mk XVI had an A tube, jacket to 63.5 inches (1.61 m) 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.

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.

[5] (list not complete) (list not complete) 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.