.308
I can find the ammo anywhere - cheap. It has as much (or as little) power as needed - especially with today's bullets and fancy powders. Short action, light recoil (I am getting older), light weight (love my Kimber 84M), and a light compact scope (Nikon Monarch 2 - 7x).
If you have what it takes (tolerance for pain, shooting skills, money, time to practice a lot, can read the wind, ...) get a fancy 7mm or 300 mag - reach way out and take one down.
In Southern MN where we must use shotguns, I am shooting a Benelli 20ga semi. The new slugs have as much power as a 45/70 and the slugs are amazingly deadly.