Re: help with 300 Win Mag.
Just a thought but you may want to do prelimiary work up with bullets like the Hornady Interlock or SST, Sierra Gameking. They are very accurate bullets and usually get good results from most rifles.
That way you save some money while working up a load and get a baseline so that you can compare the performance of the Barnes and Swift. B & S bullets can be a little finicky to work with.
Powders like H4831SC, H1000, and IMR 7828 are great powders. I like Fed 215M primers too. With heavies, the Retumbo and RE22 may work for you.
Personally, I would free float the barrel, bed the action front and rear and start shooting. You may find that it will already shoot sub MOA the way it is. If any production barrel will consistently shoot sub MOA, I am happy. Why spend extra money to true up a barrel that may never shoot tiny groups?
Use a collet die or accurate neck sizing die for best performance. If you seat good bullets straight, chances are your groups are going to be small.