The same discrepancy happens in the 9.3x57's as to groove to groove dimensions as well as body length differences from the standard 57mm Mauser case. The body needed to fit my chamber was .019" longer than the 8mm Mauser body. With soft-ball loads in the 30,000PSI to 35,000PSI range, if brass was simply necked up 8x57, in many rifles the firing of low pressure loads resulted in backed out primers due to the longer body length in the chamber producing excessive headspace.