Mauser Bolt Rifles by Ludwig Olson contains ballistics data for the 8x75 cartridge. It would be quite an effective round although needing a long action. The book shows muzzle velocities of 2722fps with a 227 grain bullet, 2709fps with 196gr, 2959fps with 185gr, 2978fps with 154gr and several other loads. Also gives powder charges and other ballistic data for this cartridge. The narrative says it was the longest and most powerful of the commercial 8mm cartridges. The photo in the book of the cartridge appears to be of the rimless version although it is not stated anywhere that there was a rimmed version and the DWM ballistic data does not identify which version the loads are for (10 loads in total.)

When I was in Germany my friend was fire-forming cases and working up loads for his single shot 8x75 rifle. I can't recall what the rifle was other than it was probably made in Ferlach for him and had an octagonal barrel and it was for the rimless cartridge.