RE: Rifle build,which caliber?
I would opt for the .300 Win Mag., if I wanted a good all around big game hunting rifle. If wanted something a little out oif the ordinary or different, I would consider the7mm STW. Yeah, the 7mm STW has it beat in speed and a tad better trajectory, but it's just awful hard to beat a good shooting .300 Win Mag for all around big game hunting. There is also more handloading/reloading options for the .300 Win Mag and not to mention the variety and availability of factory ammo.
BTW, You cannot and will not go wrong with a Hart barrel. It's is as good as any and better than most on the market. Don't let anybody tell you other wise.