8 x 57R/360 was only a guess. It may have originally been any one of a dozen, now-obsolete 8 mm's. If it were the 360, it was not necessary to rechamber it. Custom-loaded ammo is still available in Germany, from Wolfgang Rohmer I think. Plus it's easy to make up the brass from 9.3 x 62R which is what I did with mine. Also, Norma, 196 grain, .318 diameter, jacketed soft points, still turn up at gun shows here, I bought 2 boxes of 50 last year for $20.