RE: 7MM Rem Mag Ammo
My Savage M110 7mm shoots everything well (under 1 MOA). The Winchester Supreme 150 grain BST shoot super tight groups (sub-MOA past 300 yards) in that rifle and Federal Premium 160 grain Nosler Partitions only slightly larger groups (and absolutely devestating on everything I have shot with it).
IMO, the 7mm is generally a very accurate cartridge regardless as to the factory ammo maker. Find a round that your rifle likes, you are comfortable with, and can readily purchase.