RE: Best 7mm Rem Mag cartridge for Elk??????
Accurate bullet placement should be your primary consideration, followed by use of the proper bullet for the game you are hunting. Get 2-3 different cartridge/bullet combinations to try. The one that shoots the best groups is the one you should hunt with. For example, some rifles shoot some cartridge/bullets great (say Federal Premium cartridges loaded with a 160gr Nosler Partition) while they won't group others (say Win Supreme loaded with a 160 gr Failsafe) worth a darn. You would be wise to see which cartridge/bullet your particular gun likes. Elk are taken every year with 7mags using 150 gr and up, so don't get hung upon the bullet weight. Accurate placement of a suitable bullet brings home the bacon every time.
Good Hunting,
Hal