Very interesting discussion. It is well established that at certain velocities water acts as a solid due to his incompressibility. The first I heard about that concept was as a child when my father explained that to me that when I wanted to jump off something high into the water, a fact that was drilled into pilots in parachute school. That's what kills people who jump into the water off bridges high enough for them to reach near terminal velocity before hitting the water surface.
Look at water jugs or watermelons. At some cross section/velocity the bullet just goes straight through, at another the water jug or watermelon will explode. Small, pointed and boat-tailed rounds moving really fast really penetrate. Larger caliber pistol wad cutters tend to cause explosions (I loved finding over ripe melons and cucumbers in my grandparents garden). I would anticipate that somewhat similar effects occur in a mammal. However, skin does a really good job of keeping everything together which is I would guess is why we don't see abdomens exploding from certain rounds.
I'm sure that at the major ammo manufacturers they have engineers who have worked out all this stuff and there are probably ballistics formulas, I would guess based on fluid dynamics, that are used to calculate the balance between bullet weight, cross section, shape and velocity. Still, as with any commercial enterprise, that doesn't mean that a product that doesn't quite do what it is advertised to do in quite the way it is advertised to do it isn't marketed.
