Pistol bullets really arent great stoppers. There is a reason that hospital emergency rooms successfully treat Gun Shot Wound patients on a regular basis. Having talked to many EMTs and trauma doctors, and examined a significant amount of pictures/medical reports, there is a negligible difference between the wounding capacity of the 9mm and the .40 S&W. The idea of energy transfer is misplaced in regard to wounding potential because the net amount of energy contained in a pistol bullet is pretty low when we think about really having dramatic effect on a human body (knocking someone down, for example). The damage that is done is created through cutting and crushing. The difference of a few grains of weight, a few feet per second of speed or a millimeter (literally) of diameter are not worth giving up on the faster strings of fire or the higher capacity mentioned above. While the .40 S&W round, especially in heavier versions, has more potential for penetration of intermediate barriers, the data on actual personal defense shooting suggests overwhelmingly that there are not likely to be any hard barriers to be penetrated. (Law Enforcement Officers face barriers much more often, presenting a stronger argument for the .40 in the role of police duty gun). Tom Givens Lessons From the Street DVD is a great example of real world self defense shooting data of the type that should be influencing our choices.
Oh where to start...... sometimes the "facts" and "science" should be best left for those that actually have a background in it. Rather, I'd love for him to prove that damage doesn't occur incrementally, especially in regards to bone and tougher tissue, considering his barrier comments.