QF 2 pounder naval gun

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For the 2 pounder anti-tank gun see Ordnance QF 2 pounder

The 2-pounder gun, officially designated the QF 2-pounder (QF denoting "quick firing") and universally known as the pom-pom, is a large calibre British machine-gun, used mostly famously as an anti-aircraft gun by the Royal Navy. The name came from the sound that the original models were reported to make when firing. Although these were 2-pounder guns, in that they fired a projectile with a weight of 2 pounds, they were not the same gun as that used by the British Army as an anti-tank weapon or to equip British tanks and certain armoured cars.

[edit] Boer War and the Great War

The first gun to be called a pom-pom was the 37 mm Nordenfelt-Maxim introduced during the Second Boer War, the smallest artillery piece of that war. It fired a shell one pound in weight accurately over a distance of 3,000 yards. The barrel was water cooled and the shells were belt-fed from a 25 round fabric belt. The Boers used them against the British, who, seeing their utility, had the design copied by Vickers, who were already producing Maxim guns.

In World War I it was used in the trenches of the Western Front against aircraft. It was common British practice at this time to refer to artillery by the weight of the projectile rather than the bore of the barrel, e.g a 3-pounder gun had a calibre of 47 mm, a 6-pounder was 57 mm etc.

The first naval pom-pom was the QF 1.5-pdr Mark I, a piece with a calibre of 37 mm (1.46 in) and a barrel 43 calibres long. This was trialed in the Arethusa class light cruisers HMS Arethusa and Undaunted, but did not enter full service, being replaced instead by a larger weapon, the QF 2-pdr Mark II (see below).

[edit] QF 2-pounder Mark II

The QF 2-pounder Mark II was essentially a scaled-up version of the 1-pounder Maxim gun produced by Vickers. It was a 40 mm calibre gun with a water-cooled barrel and a Vickers-Maxim mechanism. It was ordered in 1915 by the Royal Navy as an anti-aircraft weapon for ships of cruiser size and below. The original models fired from hand-loaded fabric belts, although these were later replaced by steel-link belts. This 'scaling-up' process was not entirely successful, as it left the mechanism rather light and prone to faults such as rounds falling out of the belts.

Surviving weapons were brought out of storage to see service in World War II, mainly on board second-rate ships such as trawlers, Motor Boats and "armed yachts". It was used almost exclusively in the single barrel, unpowered pedestal mountings P Mark II (Royal Navy nomenclature confusingly gave mountings and guns their own distinct Mark numbers) except for a small number of weapons on the mounting Mark XV which was a twin-barreled, powered mount. These were overweight and cumbersome and too heavy to be of any use at sea and were therefore mounted ashore. All were scrapped by 1944.

• Calibre: 40 mm L/39
• Shell Weight: 2 lb. (980 g)
• Rate of Fire: 200 rpm
• Effective Range: 1,200 yards (1,000 m)
• Muzzle Velocity: 1,920 feet/second (585 m/s)

Some 7,000 guns were made. The gun was also used by the Japanese as the 40 mm/62 "HI" Shiki.

For more extensive technical data see 2-pdr Mark II at Navweaps.com

[edit] QF 2-pounder Mark VIII

The quadruple 2pdr. mounting Mk.VII of HMS Kelvin seen in action during the Mediterranean campaign.

The Royal Navy had identified the need for a rapid-firing, multi-barrelled close-range anti-aircraft weapon at an early stage. Design work for such a weapon began in 1923 based on the earlier Mark II, undoubtedly to utilise the enormous stocks of 2-pounder ammunition left over from World War I. Lack of funding led to a convoluted and drawn-out design and trials history, and it was not until 1930 that these weapons began to enter service. Known as the QF 2-pounder Mark VIII, it is usually referred to as the multiple pom-pom. The initial mounting was the enormous, 16-ton, eight-barrelled mounting Mark V (later Mark VI), suitable for ships of heavy cruiser and aircraft carrier size upwards. From 1935 the quadruple mounting Mark VII, essentially half a Mark V or VI, entered service for ships of destroyer and cruiser size. These multiple gun mounts required four different guns. The mount had 2 rows each of 2 or 4 weapons. Guns were produced in both right and left hand and "inner" and "outer" so that the feed and ejector mechanisms matched. Single barrelled mounts, the Mark VIII (manual) and Mark XVI (power operated), were also widely used, mainly in small escorts and coastal craft. The Mark XVI mounting was related to the twin mounting Mark V for the Oerlikon 20 mm cannon and the "Boffin" mounting for the Bofors 40 mm gun.

An advanced weapon when introduced, by the outbreak of World War II advances in aircraft had effectively made it obsolete. It was intended that the curtain of fire it threw up would be sufficient to deter attacking aircraft but lack of a suitable tracer round meant that the barrage was unseen and so the deterrence factor was prevented from being effective. It had a low velocity due to the relatively short barrel and small charge, the fuse mechanism was unsatisfactory, the weapons were extremely complex and prone to jamming, and the mountings were enormously heavy and complicated and could not be produced quickly enough or fitted widely enough. When HMS Prince of Wales was attacked and sunk by Japanese aircraft near Singapore the subsequent report judged that the single 40 mm Bofors gun, mounted on the quarterdeck, had been a more effective anti-aircraft weapon than the entire battery of multiple pom-pom mounts. Nevertheless, it was a ubiquitous weapon that was never entirely displaced by the Bofors gun during World War II. Later innovations such as remote power control (RPC) coupled to an effective radar-equipped tachymetric (speed predicting) director increased the accuracy enormously, and problems with the fuses and reliability were also addressed. The single mountings received a reprieve towards the end of the war, as the 20 mm Oerlikon guns had insufficient stopping power to counter Japanese Kamikaze aircraft and there were insufficient numbers of Bofors guns to go round.

• Calibre: 40 mm L/39
• Shell Weight: 2 lb. (980 g) or 1.8 lb. (820 g) for High-Velocity (HV) round
• Rate of Fire: 115 rpm fully automatic
• Effective Range: 3,800 yards (3,475 m) or 5,000 yards (4,572 m) HV
• Effective Ceiling (HV): 13,300 feet (3,960 m)
• Muzzle Velocity: 1,920 feet/s (585 m/s) or 2,300 feet/s (701 m/s) for HV

For more extensive technical data see 2-pdr Mark VIII at Navweaps.com

[edit] QF 2-pounder Mark XIV

The QF 2-pounder Mark XIV, or Rolls 2 pounder, was developed by Rolls-Royce as a competitor to the 40 mm "Vickers S" gun as an aircraft weapon. The latter was the more successful design, and found some use as an anti-tank weapon. A reworked version was adopted by the Royal Navy as a weapon for Motor Gun Boats, being adopted in the Fairmile C type. It had a semi-automatic horizontally sliding breech block, and was shipped on a manually trained pedestal mount. The weapon was not a success, and of the 1,200 ordered only some 600 were delivered. It was replaced by the Molins 6-pounder (57 mm) gun, the Army's Ordnance QF 6 pounder gun with an auto-loader.