This is my fourth bison hunt over the past 22 years. As previously mentioned, I used my .338 Winchester mag. It seemed to dispatch this beast adequately. Previously, I used a .30-06, a .458 Winchester mag and a .458 Lott. Of the four cartrages I've used, the .458 Win mag and .458 Lott were most effective, equally. In both incidents the animals dropped straight to the ground without moving, not so with the lighter loads. Both the .30-06 and .338 took multiple shots to finish the job.

Regarding a head shot, unfortunately I didn't think to do that but I did get this photo of the bison right after the kill. I apologize that it is in black & white as I didn't notice the camera setting until after the fact.

By the way, I also have .45-70 Govt. (the original cartridge developed in the 1800s for shooting bison) in a double rifle that I may consider using for a future hunt, pocket book pending.