I've found the .22 mag. quite effective on foxes out to 125-150 yards so long as you and your rifle are capable of putting bullets in the vitals. On our big Northeastern coyotes it depends on what you consider "effective". If you've got snow on the ground and don't mind tracking them aways then it's effective as far as it is on foxes. If your idea of "effective" is that you expect them to drop right now with shots through the chest cavity you need more gun. Of course head shots will plant them on the spot.