"Once the basic recoilless principle had been proved, work also began on a monster gun in response to a request from the Luftministerium for an anti-ship weapon capable of firing a 1,400lb. armour-piercing shell to penetrate battleship deck armour. The object was to use this to bombard the British fleet as it lay at anchor in Scapa Flow. The result of this was Gerat 104 ('Equipment 104'), a 35cm calibre gun slung beneath an aircraft and retracted hydraulically during flight. With a weapon of this size, a jet efflux would doubtless have wrecked the carrying aircraft completely, so the Rheinmetall engineers went back to the Davis' idea and produced a counter-shot weapon. Instead of using a second barrel and a special counter-shot, the same result was achieved by making the cartridge case with a heavy steel casing which weighed 1,400lbs, the same as the armour-piercing shell. As the cartridge fired the shell forwards, so it fired the cartridge case backwards, achieving the necessary balance and recoillessness. Obviously, reloading a 1,400lb. shell plus a cartridge of equal weight while in flight was out of the question, so the Gerat 104 was strictly a one-shot weapon. But before flight trials could take place, war broke out, and since it was thought that other things were more important, further development of the Gerat 104 was stopped." ~ Ian Hogg

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