From memory both the 8.5x63 & 8.5x63R are based on 7x64 & 7x65R brass.

Id be keen to see some "real" ballistic data for the rimmed version in a short barrelled drilling or kipplauf.
In theory it should be capable of >2700fps with a 200g bullet putting it in front of the 8x75RS and .30R Blaser, two cartridges that have the reputation of needing 65cm barrels to achieve their factory listed velocities.