I have a line (at a great price) on a Pre-64 Model 70 that somebody has rechambered (and re-barreled) to .358 Norma Mag My question is: How hard would it be to re-chamber to .358 STA? They both use the same rime thickness (.048). They're both belted magnums using a rebated rim. The head dia. of the .358STA is only .005 larger (.508 to .513). The shoulder dia. of the STA is only .007 larger. Is it just a matter of re-cutting the chamber? I'm hoping one of the Gunsmith Gurus will lend their expertise.