If I had to do over again, I'd go with the 300 Win. mag. over the 7 mag. but I got a really good deal on my rifle, so I'll keep it for now. I'm going to put a muzzle brake on it this spring. So I can follow my shots better.Go with the .300 Win mag.
It is my personal opinion but I believe that the short mag craze will die out and if you don't reload you may have a hard time finding ammo.