You will need to cast the chamber & slug the bore as other have suggested to determine the true cartridge, if it was based on the 43 mauser 11.15x60R case there are approx 130 variations based on that MB case. I have a Buchsenflinte (cape gun) that is
a 10.25x60R that I had to reform from 43 mauser to fit my gun.
Dietrich Apel & Steve Meyer are a wealth of info and very helpful
follow their advise & join the German Gun Collector Assn if you have an intrest in these type of guns and you will be rewarded with the satisfaction of putting a 110 years old gun back into service that you will enjoy until you pass it down to the next generation to enjoy, if you don't think your up to all that then
sell it to someone who is so these fine guns don't become lost forever.
m-4
