You are right, "8.9 mm" converts to a bore or land diameter between .350" and 9.0mm = .354", but this is the bore, not the rifling diameter. this was measured at the proofhouse using a cylindrical plug gauge. To get at the bullet diameter, you have to add two times the groove depth!Now, 8.9mm is correct for a 9.3mm cartridge. "62" is the case length, so your rifle is indeed chambered for the 9.3x62. As the bore diameter is given in mm instead of a gauge number, fi "108,49", your rifle was proofed 1912 to 1939. There should be another three-digit number like 5.28 giving month and year of proof.