A fellow I knew when we lived in Colorado twenty years ago shot most elk with a 6mm Gibbs. Used 75 grain hollow points (which was an illegal bullet in that State for elk), shot them in the lungs and waited for them to die. He was a three State hunter and during the time I knew him he usually got three elk a year. His was a neurosurgeon and probably knew the anatomy of elk too, and only took shots that he was able to place where he wanted them.