QF 4-inch naval gun Mk V

The QF 4 inch Mk V gun was a Royal Navy gun of World War I which was adapted on HA (i.e. high-angle) mountings to the heavy anti-aircraft role both at sea and on land, and was also used as a coast defence gun.

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 Arethusa-class cruisers, was soon adapted to a high-angle anti-aircraft role. It was typically used on cruisers and heavier ships, although V and W-class destroyers 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Mk V was superseded by the QF 4 inch Mk XVI as the HA (i.e. anti-aircraft) gun on new warships in the 1930s, but it continued to serve on many ships such as destroyers, light and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.

Ammunition
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. The fixed Mk V ammunition was 44.3 inches (1.13 m) long and weighed 56 pounds (25 kg), while the projectile was 31 pounds (14 kg).

Weapons of comparable role, performance and era

 * Cannon 102/45 Italian copy of the QF Mk V made under license
 * 10.5 cm SK L/45 naval gun Approximate German equivalent firing slightly heavier shell

Surviving examples

 * A gun from HMNZS Tutira in front of the Devonport Naval Base, Auckland, New Zealand