My boss told me when he first started hunting in CO he went out with a 30-30. He spoted a deer and put one in the kill zone and the deer ran up and over a hill. When he got over the hill he found 2 other hunters gutting it with their tag already on it.
When he got back home he bought a 300 win mag......
Personally I would use a higher power cartridge. 300WM is a bit overkill but I personally prefer a .308 win