It's definitely NOT the 7mm mag. That cartridge has way more than enough power to drop anything on the North American Continent. I have heard some people complain about the TTSX bullet while others rave. I personally use a 7mm.08 for whitetail with hand loaded 139gr Hornady Interlocks with beautiful results. Have taken several Elk with that combination as well so I would have a hard time believing that a 7mm mag would have a problem with a Muley.