I guess another way of looking at then is the animal has potential energy that becomes kinetic energy when struck by the bullet which is probably the more accurate way of putting it, which means the larger the mass and higher the velocity the greater the effect on the potential energy stored in the flesh and fluids of the animal. How can you say that an expanding bullet dosn't create a larger shock wave when it expands. It is true that energy just changes forms and that it is constant in any object but changes from potential to kinetic and in this case actually also heat. Like I said earlier run your fist through water or stick it out the window at 65mph and then open it up and see how much the resistance increases. The fact is still no matter how you word it that an expanding bullet has a higher shock value if it works properly which is why all true man stoppers are hollow points. My wording may be off from being rusty but the principle is the same, when a bullet hits an animal there is an internal shock wave and the frequency and amplitude of that shock wave are determined by the bullet that strikes the animal. I also guess a better way of putting one of my earlier statements is that the bullet is expending it's energy inside the animal as it returns to a static or potential state and the more energy expended inside the animal as it passes through the better as long as penetration is there. No different than hitting a sink full of water lightly with your fist or slapping the surface of the water as hard as you can with your palm. Because of the makeup of an animal we are basicly dealing with hydraulics which also brings in cavitation which all involves the displacement of fluid which can be violent enough to destroy organ tissue.