for the Oerlikon 20 mm cannon and the "Boffin" mounting for the Bofors 40 mm gun. Magazines ranged from 140 rounds per gun for the eight-barrelled mount to 56 rounds for the single mounts. This large ammunition capacity (1,120 rounds) gave the eight-barrelled mount the ability to fire continuously for 73 seconds without reloading. A high velocity (HV), 1.8 lb (820 g), round was developed for the pom-pom, just before the Second World War, which raised the new gun muzzle velocity from 2,040 ft/s (622 m/s) to 2400 ft/s (732 m/s). Many older mountings were modified with conversion kits to fire HV ammunition, while most new mounts were factory built to fire HV ammunition. A mount modified or designed for HV ammunition was given a '*' designation; for example a Mk V mount modified for HV ammunition would be a Mk V*. US Navy The United States Navy also considered adopting the pom-pom gun prior to its entry into the Second World War, and conducted a series of trials between their own 1.1" gun, the U.S. Army 37 mm Gun, the Vickers 40 mm pom-pom, and the Bofors 40 mm: Wartime use Although an advanced weapon when it was introduced, by the outbreak of World War II advances in aircraft would have made it obsolete but for the introduction of the high-velocity round and new director designs. It was intended that the curtain of fire it threw up would be sufficient to deter attacking aircraft, which it did, but was hampered by the ineffective Mk III director. The MK IV Director with a Gyro Rate Unit and Type 282 radar was a great advance and was introduced on the King George V-class battleships. In January 1941, ′s Mk VIII (HV) mountings performed flawlessly firing 30,000 rounds with very few stoppages. When was attacked and sunk by Japanese aircraft near Singapore, the subsequent report judged that a single 40 mm Bofors gun firing tracer was a more effective anti-aircraft weapon than a multiple pom-pom in director control, as the pom-poms did not have tracer ammunition and the pom-pom ammunition had deteriorated badly in its ready use lockers, while the Type 282 radar units also failed in the equatorial heat. In the same action, the Commissioned Gunner of spent the whole action running from one pom-pom mount to another trying to keep them operational due to the faulty ammunition. The pom-poms on