My son was given a 1903 (Argentine?) Mauser chambered in .30-06. All serial numbers, including barell, matched. The barell appears to be factory marked as .30-06. It doesn't shoot worth a crap, and the casings show "ridges" on the shoulder as if the chamber reamer was really worn out. Any suggestions for a decnnt fix? I thought maybe rechambering to .30-06 A I might be plausible.