Of a similar vein - what about all those weird and wonderful Webley recoilless rifle prototypes that appeared in the Wallis & Wallis (2006) auction? Several were bought by the owner of Target Sports in Bolton and, as I worked ( ) there part time, I had the pleasure of playing with several of these plus other weird guns. For example there was a pre charged rifle that you filled by inserting the probe into the end of the barrel. It took us a while to figure that one out. Then there was the prototype Omega (which eventually came home with me) a adjustable gas rammed Omega and Vulcan (again they found their way into my gun room ) but I could never afford the recoilless rifles. Many went back into another auction (Holts?) a few years later when the shop closed.
I still have the catalogue from the W & W auction.
ATB
Ian