This QF gun was introduced to provide a higher rate of fire than the BL 4 inch Mk VII.

It first appeared in 1914 as secondary armament on Arethusa-class cruisers, was soon adapted to a high-angle anti-aircraft role.

Mk V was superseded by the QF 4 inch Mk XVI as the HA (i.e. anti-aircraft) gun on new warships in the 1930s, but it continued to serve on many ships such as destroyers, light and heavy cruisers in World War II.

The AA mounting allowed elevation to 80° but loading was not possible above 62°, which slowed the maximum rate of fire.

[7] Ammunition for the original low-angle guns introduced in World War I was Separate QF i.e. the shell and cartridge were separate items, but in World War II most guns used Fixed QF ammunition i.e. a single unit.