I wouldn't call a 22-250 weird either; just hated to think of making a PPC work as a "first project". I'd think a 250-3000 could be made to work as well.

One other question; are you new to machining altogether or just the particulars of gunsmithing? Buying a pre-contoured barrel can be worth the money if you want to minimze how much new stuff you've got to absorb on one project.

I think Gun Parts Corp sells a kit convert a Mauser to 7.62x39. I have a Mexican 1910 that was converted, it feeds very well, holds 6 in the magazine. They welded up the extractor to make it work.