I luv the 7mm Mag, one of my favorite LONG range rifles. For the hunting you described, I think you're over guned and way over scoped. Even on 3x, in cover, you're will most likely hate how hard it's going to be to find your target at 50 yards, especially after you have a big buck or two walk off while you're still trying to find them in the scope.
As mentioned before, magnification is not the key, the quality (clarity) of the lens is a key point of what makes a good scope. Just the other day I was in a gun store and they had a used, Weaver 2.5X scope sitting on a shelf with a Japan Tasco 2.5-10x42 AO wide angle scope. I wanted the weaver for my granddaughters 22 and he sold me both for $15. I figured the Tasco would make a good scope to put on some cheap, beater gun. After all, the very first scope I ever bought was a Tasco 3-9x36 and it was a nice scope. I put this Tasco on a 22 just to play with it. This Tasco is absolutely the worst scope I have ever seen in my life. At 100yds on 10x, if you adjusted the eye focus so the cross hairs were clear, the target was almost totally fuzed out. If you adjusted it so you could see the target (no such thing a clear) then the cross hairs were so blurred, it looked like there's a half dozen of them. When it came to eye relief, there was none, it felt like my eye was no more than 2" from the scope. If this is what you get for a cheap scope, people need to start looking through a real scope and see what they are missing.