The best literature that would describe these actions should be Greener's The Gun and its Development in one of the recent updated editions. I have, however, invited the new Greener company to comment on the Facile Princeps design as well as their relaunching of the Unique ejector system - these are the first guns being made to these grand old designs after WWII. I hope that they would respond soon.
Best wishes,
-------------------- The Ark was made by amateurs. Experts built the Titanic.