BL 4 inch naval gun Mk VIII

The BL 4-inch gun Mark VIII was a British medium-velocity wire-wound naval gun introduced in 1908 as an anti-torpedo boat gun in smaller ships whose decks could not support the strain of the heavier and more powerful Mk VII gun.

Mk VIII History
The gun succeeded the QF 4 inch Mk III, whose 25-pound shell had been considered insufficiently powerful for its intended role. The BL Mk VIII fired a 31-pound shell. It armed the following warships :
 * HMS Swift (1907) laid down 1905
 * destroyers from HMS Saracen (1908) (1908) onwards.
 * of 1909
 * s of 1910
 * s of 1910
 * s (Australia) of 1910.

The gun was succeeded in its class from 1911 by the QF 4 inch Mk IV.

In World War II many guns were used to arm merchant ships.

Mk XI submarine gun
A Mk XI variant was adapted to arm submarines :
 * K-class submarines laid down 1915