and I still believe its a nutria

don't believe the 8x72R Brennecke starts as a black powder round.
must be one of the first Brennecke caliber in history the biggest advantage was the low pressure suitable for the early guns made then for nitro cartridges. they were learning then slowly by broken guns that nitro rounds needing stronger actions on the long run than what they build before for black powder cartridges all the years.