hallo
what we know: is it a real 10mm /400 and it have a paper thin neck
there are very few 10mm cartridges in germany/austria. beside of the 10x60R 400 only some 10 mm target rounds bases on the 11,15 x60R mauser brass. there are maybe also other wildcats from this time I did not know but...
the paper thin brass case is typical for the early express rounds and the 10x60 R 400 comes from one. this is not a 450 basic case necked down. the 10,3x60R swiss is such a thing.
ok, the camber seems to be to short for a 60 mm long case but maybe it fits. old chambers are made different than we do it now. I have casting were the chamber ends with the case mouth. no free bore, nothing, the lead bullet engrave into the rifling when loaded.
I can only tell you what I would do: talking with cartridge collector for getting an original 10x60R 400 from Georg Roth and try to load it. I dont know if this is a problem for you, can only tell you that I would get it here in some days.
the 10x60R 400 was the only standard factory 10 mm cartridge and it was popular around the turn of the century
![](http://up.picr.de/7461328fwo.jpg)
franz sodia ferlach
![](http://up.picr.de/7461329awq.jpg)
georg roth 1927
original bullet weight was around 250 grains. i think you will find something for the 10 mm auto