The single most impressive kill on a running mule deer that I have witnessed was when I was 17 years old. (The incident was more than too much for an overly impressionable me, by the way.) Efficent doesn't even begin to discribe the kill. More like the hands of the gods all came down and slapped that deer to the dirt. The rifle is currently for sale on the net. Caliber is .475 #2.

Just because they were designed for big DG in mind, does not make them any less exceptional in use on smaller non-DG in my opinion.