From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
The future requirements for aircraft cannon guns, comparing the ballistic merits of 6-pdr and 12-pdr variants.
| Identifier | ExFiles\Box 176\1\ img226 | |
| Date | 9th November 1942 | |
| Gun Files To: Ve. from Rm.{William Robotham - Chief Engineer} c. to Sg.{Arthur F. Sidgreaves - MD} c. to Hs.{Lord Ernest Hives - Chair} AIRCRAFT CANNON GUNS - FUTURE REQUIREMENTS. I have now received the report from the ballistic section on the relative merits of the 6-pdr gun at 2850 f.s.m.v. and the 12-pdr. gun at 2200 f.s.m.v. when both are fired from an aircraft having a forward velocity of 300 f.s. You will note that they consider the 12-pdr. to be a far better proposition and much less likely to be subject to shatter. You will also note that they expect 12-pdr. to penetrate 120 mm. of armour-plate at normal at 300 yds. range which, I think, is an ample performance to deal with any Armoured Fighting Vehicle which is likely to be produced by the Germans in this war. The 12-pdr. has an added merit in that it can carry a really useful bursting charge which is greatly favoured by the Americans, Germans and the Russians for anti-Tank work but, up to the present, has not been a feature of the British anti-Tank weapons owing to their small calibre. The history of the ultra-high velocity taper bore Little John development is that it would probably never have got into production had it not been for the fact that thousands of British Tanks were equipped with 2-pdr. guns which were incapable of piercing the latest German frontal armour. The correct answer to this was really the 6-pdr gun, which meant a new Tank, but converting the 2-pdr into squeeze-bore guns gave some relief. The same reasoning might apply if the Boche produced a Tank which cannot be dealt with by the existing 2-pdr aircraft cannon before a heavier gun is available. The only reason the projectile of the ultra-high velocity gun does not break up is because it is made of tungsten carbide. The small quantity of this available would preclude its being used in anything appreciably bigger than about 27 mm. sizes or less. Report enclosed. Rm.{William Robotham - Chief Engineer} | ||