25-06 or 22-250 there is prob more 22-250s used for varmit hunting than any other caliber seems that no matter what brand it is the 22-250 is a accurate rifle no recoil and nice range will usually shoot farther than most can see at night i personally like my 5mm rem for varmits
25-06 would leave to big a hole on the exit wound IMO I shoot deer in the neck with mine and it leaves a fist sized hole I use remington core lock 100 gr