Re: 7mm Remington Mag or .308
You cannot go wrong with either of them. Both of those will get the job done, but in my opinion the 7mm Rem Mag gets it done a little better. The 7mm has plenty of knock-down at that range, and that caliber bucks the wind better than most others.
However, if you are sensitive to recoil, go with the. 308. You really can't lose with either choice