QF 4-inch naval gun Mk XIX

The QF 4-inch Mk XIX gun was a British low-velocity 4-inch 40-calibre naval gun used to arm small warships such as and and some in World War II, mainly against submarines.
Description.
It succeeded the higher-velocity World War I-era BL 4-inch Mk IX (typically deployed on s in the escort role). The Mk XIX fired fixed ammunition which was long and weighed . The weight of the projectile was increased from for the Mk IX to for the Mk XIX. The high-angle mounting used for the XIX added some anti-aircraft capability and allowed it to fire starshells to illuminate the battle area at night.