File:Stubbert's Point Twin Six-pounder Gun c1945.jpg

Stubbert's Point quick-firing Twin Barrel (duplex) Six-pounder Gun (QF 6 pounder 10 cwt gun) in its steel turret, ca. 1945. These semi-automatic loading, duplex guns (dated 1943) could pour out seventy rounds per minute; on Malta these same weapons were to play a vital role in the successful defense against an attack of that Mediterranean island by nineteen Italian MAS fast attack boats on 26 July 1941, when five enemy boats were sunk in less than two minutes.

Weight 1,060 lb (481 kg) Length 9 ft (2.787 m) Barrel length 47 calibres Crew 6 Calibre 57 millimetres (2.24 in) Recoil 12 inches Elevation -10/+80 Traverse 360 degrees Rate of fire 70 rounds per minute Effective firing range 11,300 yards (10,330 m) @45°

During the 1920s a specification was issued for a harbour defence gun with a higher rate of fire than the 12-pounder for firing against fast-travelling torpedo boats. After investigations it was decided to adopt a twingun mounting capable of a high rate of fire and the first prototypes were under test by 1928. Series production began in 1934 and the guns remained in service until 1956.

To achieve the required high rate of fire (at least 30 rds/min) the guns were provided with a revised firing system. The two aimers carried out their aiming duties continuously and did not actually fire the guns. That function was carried out by the loader who actuated a firing lever as soon as each round was fully loaded into the semi-automatic, vertically sliding breech mechanisms. With a trained crew fire rates could be as high as 40 rds/min from each barrel – some crews could manage better.

The two 6-pounder barrels were placed side-by-side on a fixed pedestal in a concrete emplacement that usually restricted the traversing arc, which could be up to a full 360° when unhindered. The guns were protected by by a wide armoured box housing open to the rear to enhance ventilation during prolonged firing sequences.