Naval service 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 s, was soon adapted to a high-angle anti-aircraft role. It was typically used on cruisers and heavier ships, although s of 1917 also mounted the gun. Mk V was superseded by the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.
Army anti-aircraft gun Early in World War I several guns were supplied by the Navy for evaluation as anti-aircraft guns for the home defence of key installations in Britain. They were mounted on static platforms and proved fairly successful after a
fixed round was developed to replace the original
separate round, and more followed. The AA mounting allowed elevation to 80° but loading was not possible above 62°, which slowed the maximum rate of fire. At the
Armistice, a total of 24 guns were employed in AA defences in Britain and 2 in France. After World War I, the guns were returned to the Navy.
Coast Defence gun From 1915 to 1928, several guns were mounted in forts to guard the estuary of the River Humber. ==Anti-aircraft performance==