The caliber I'd think about would be the 6.5-06, which is like the 260 Remington with a little extra muscle. The recoil would be reasonable, so that practice wouldn't be unpleasant. I'd then get a really good rangefinder and a really expensive scope with dial-the-distance turrets. All that would be wasted, however, on somebody that hasn't hunted and target shot for years (a comment NOT aimed at the OP). That'd be a decent set-up for deer, coyote, and pigs. I doubt that's enough power for larger animals. As for shooting game at 500 or 600 yards, that's up to each person, but I"ll pass. I'll shoot at a coyote at 400, but I keep the deer shooting at about 300 max, and only if it's under ideal conditions. For me, 500 yards is just out of the question for several reasons.