yeah yeah yeah yeah 436...see? THATS THE KIND OF ANSWER I NEED!! so it would need to be a bolt face similar in size to a 300 mag? or does it have to be 300 H&H mag?
It can be either. But the better choice would be a 7mm Mag Like I said; it works better if you're in the same cartridge case body diameter on the feeding rails of the action and the cartridge follower. Just one more thing you don't have to mess with.
From what I've found buying old actions and build new rifles... there seem to be more 7mm Mag in Rem 700 floating around for sale at a better price.
As WildRose said; give some thought in getting everything you can use and would want to keep in there rifle purchase... that way your just putting on the new barrel and you can have the barrel guy turn it too the same contour as the take off barrel, if you'd like saving more time and money.
Good luck on your project.
436