Tell me about it years ago my 444 Markin took 2 shots. I upgraded to 500 grain in a 450 Marlin custom bolt gun. Not that is guarantees a one shot kill but a 500 solid at 2,000 FPS will break those bones.You will need bullets that will hold together and penetrate along with proper shot placement no matter what caliber you are using. The only shots that stop them in their tracks are a brain (difficult to make) or a spinal column in the neck or shoulder area.