Mannlicher made a 8X51 Mauser, for the sporting rifle market. I have a Mannlicher-Schoenauer rifle in that caliber. So marked on the action. I was rebarreled and to put it back where it was suppose to be I ordered a reamer & headspace gages from Cramer.
It is a .318 bore instead of the 323. Problem is in reloading info, the only mention I've found in any of my reloading manuals (or on the internet) is in Col Sharps COMPLETE GUIDE TO RELOADING. The good Col says, if you have to reload this rifle, you are on your own.
Anyway the Measurements for this case is RIM; .470, CASE; 1.996, BODY:.470, NECK; .353, BULLET; .318.
CPT USAR Ret
USAMU Sniper School Oct '78
Distinguished Rifle Badge 1071