Steven:

Thanks, but can the date be narrowed with the 1893-1911 time period? Also, I have read in "Beschub-zeichen" by G. Wirnsberger that for a shotgun tube without choke proofed/proved during this measurement was made a the muzzle and not at 22cm from the standing breech, am I reading this correctly?

I would also guess the cartridge to be blackpowder version of the 11.15X60R.

KInd Regards,

Raimey
rse