I lived and hunted in CO for 14 years, took elk, deer and antelope. I don't like recoil so I use a .270 Win. with appropriate bullets for the game. I agree that the .30-06 is the best all-around caliber for North American game, but I prefer the .270anyway. If recoil is a serious problem for you, get a good Savage or Remington bolt action rifle and put a Sims Vibration Labs "Limb Saver" recoil pad on it. A quality scope is a plus, but go with 2-7x or 3-9x, and plan to spend more for the scope than for the rifle.