Most of the guys hunting cougars around here are using 17 remington, 22-250, 6mm's etc mostly varmint calibers. Doesnt take alot to kill a cougar. They are soft tissued thin skinned critters doesnt take much to get a pass through. Most folks use varmint calibers to hopefully not destroy the hides. I figured I couldnt go wrong using a 30 cal varmint bullet just a little extra smack since it will be my first time and i dont know what to expect. Hopefully the 110 grain speer doesnt do a whole lot of damage to the hide.