2 Pounder AA GUN ???????

[narwan]

Source:
http://www.quarry.nildram.co.uk/37-40mm.htm

This bit about the 2pndr AA and 1.5pndr:

The Interwar Years

Between the wars the need was recognised to equip warships with automatic cannon in response to the growing threat of attack by aircraft. The Navy not surprisingly selected the water-cooled 2 PR already available and fitted it in a variety of mountings, from single manually-operated versions weighing around 1½ tons to the huge 20-ton eight-barrelled 'Chicago Pianos' fitted to various major warships in the late 1930s. The first developed was the eight-barrel mounting, for fitting to capital ships. The four-barrel followed, mainly for cruisers and destroyers. Single barrel mountings became popular later, particularly for fitting to Oerlikon mountings to increase firepower for dealing with kamikaze attacks.

The gun originally fired a shell weighing 0.9 kg (two pounds) at a muzzle velocity of about 610 m/s but just before the war the disadvantage of such a low velocity was recognised and a high-velocity loading, firing a 0.77 kg shell at a still modest 730 m/s, was introduced. At about the same time the rate of fire was increased form 90 to 115 rpm. The weapon was sturdy but prone to jamming for a variety of reasons and needed a well-trained crew to get the best from it. These problems together with the relatively low performance led to its gradual replacement as the much superior Bofors gun became available, although it was still widely used at the end of the war and remained in service for some years thereafter.

In the 1930s a small number of 2 PR was acquired by the British Army as a stop-gap AA weapon (in a twin-barrel fixed mounting) before the Bofors gun was adopted, but these were eventually given to the Navy.

The 1½ PR COW gun was the other survivor of WW1, being tried in a variety of aircraft, mostly flying boats but also fighters. However, it never really progressed beyond experimental status and the survivors ended their days as airfield defence guns in WW2. Its significance lies primarily in the fact that it was used as the basis for the design of the Vickers 40mm Class S described below, following Vickers' acquisition of the Coventry Ordnance Works.