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).
Letter to Wing Commander Helmore detailing the development and specifications of a 40 m.m. gun.
| Identifier | ExFiles\Box 176\1\ img007 | |
| Date | 21th November 1939 | |
| Rm.{William Robotham - Chief Engineer}6/MH.{M. Huckerby} 21st. November, 1939. Wing Commander Helmore, Department OA, Air Ministry, King Charles Street, Whitehall, S.W.1. Dear Helmore, Hives has asked me to reply to your letter of November 16th. I think if you are really interested in the 40 m.m. gun it would pay you to come down and have a look at the bits and some of the experimental apparatus that we are using in its development. We can then give you any statistics you want. Briefly, the gun has so far been produced as a single shot 40 m.m. gun of about 2500 feet per second muzzle velocity, firing a projectile just under 2 lbs. weight. One of the objectives has been that it should be easy to fabricate. It has a large recoil - 16 to 18 inches - in order that the trunnion load should be reasonably light. The recuperation is by compressed air only. It is proposed to incorporate a quick firing mechanism as soon as the gun has been completed as a single shot weapon. The breech block and barrel have already been proved at Woolwich and the buffer andrecuperator mechanism will be tested in a fortnight's time. For this reason you should come down some time next week if you can manage it. It is expected that the complete weapon will weigh about 250 lbs. We hope that it will be fired from the air as a fixed weapon by March of next year in the Beaufighter, and have ascertained there will be a machine flying by the end of next year which will have a turret which will take the gun. | ||