wayne59 send me pics of his new Dreyse doublegun SN 25550 made in 1885(+/-)

very unusual with the straight "english stock" it have the new slim action and the common center fire extractor.

compare it with the old model here

" Have no idea what the gauge is but a 20ga brass hull will almost slide in and a 24ga hull is to small. "

forget the gauge system completly I think this is a - 0,70" Randschlussspiegel - cartridge, here an unloaded shell

this looks like loaded with a roundball

you will find the cartridge specification here

I will make you pics how to disassemble the gun step by step and post it here. imho, the case can be made by using 20 ga Magtech brass. I am sure you can order lathe turned brass cases with having a chamber cast but it would be hard to make them so thin the drawn magtech cases are. remember the original shell only had a paper body.
my tool maker will made me a special sizing die for this job but he is a little bit overloaded with work so it needs some time. the small muzle loader caps will give the best primer. I deepen the primer pocket a little bit and put the cap upside down in it, than filled with fine gun powder. close the primer pocket with self adhesive aluminium foil whats no problem for the needle.

here for example in a 16 ga paper shell, fits in the bigger 0,74" Randschlussspiegel cartridge