I'm not much of a hunter, and have never hunted varmints, but I've got a couple of Savages, a 10FP in .308 and a 112BVSS in .30-06 Either of them would be great varmint rifles, and out to very long ranges. I suppose my AR would do the job too, if I put on the 20" upper and the scope.
If I'm working towards the end of this year, I may do some coyote hunting on a friend's farm in Missouri.