cayugad
Dave, back in the early 1970's National Muzzle Loading had a group testing a number of ballistic items that were going to be put in there manuel, one of those was the minimum energy that would efficiently take whitetail deer.
What they came up with is 800ft pounds. I personally believe that there are other things that enter into it as I have stretched my 54 beyond that point and still drop them on the spot. hitting the right spot is in my opinion the most critical thing. Lee