If the chamber cast suggests an 8x60 but the chamber is short, then just have the chamber lengthened properly. It's a great cartridge. You say a chamber cast indicates an 8mm. A proper chamber cast should also give you chamber dimensions. What 8x60 cartridge did you have trouble closing the bolt on?
An 8x57 Mag box is long enough for factory length 9,3x62 cartridges.
