Re: Rem 700 Barrel and Bolt Swap
Would just buy a 7-08 tube in same contour and fire it up or rechamber to 284Win and be done. If you went to the 284 there should be no headspace issues, just barrel stamp indexing if he even cares...
Should be ready to go for under $150. Keep the stock, bolt and such. Leave the action alone and he can re-install the 6mm tube when he gets bored. Would have smith pin the lug though so it stays indexed to the receiver when swapping barrels.
If it wont die with a 284 dont think it would period. Plus there is excellent brass available....