Hydro-static-shock involves the shock, or pounding, those tissues receive when water is forced aside by explosive compression of tissues because of impact. In truth, hydrostatic shock is horribly overrated. Any bullet causes impact and "shock" as it passes through and displaces water and tissue, but it may be minimal to almost non existent. Some rounds will literally explode into fragments.
Shock itself can cause bruising and breakage of small blood vessels or other tissues, but that doesn't really make much difference until you have increased your velocities between levels by 300 fps, maybe. the .45 acp is about 850 fps and the colt is about 1,100, and if you check with most people, they will agree that they will both cause about as much damage in a solid slug. It takes a large increase in velocity for a solid slug to be improved by velocity alone.
Frankly, i feel that there are other more important things to consider. Bullet design, and whether or not the ammunition is appropriate for the expected use. Shock is a nice thing, it causes pain, bleeding, etc, but what really kills things/people is either destruction of organs or vital areas, or bleeding. No matter how much shock you put into a chunk of butt with a varmint cartridge, tearing out a half pound of meat won't kill a man. same thing goes for hitting him in the butt with anything, pretty much.
When you get chest cavity hits, punch holes through innards and lungs, veins, etc, you have started the ball rolling. an expanding bullet makes the hole bigger and it displaces more water as it goes through. the faster the bullet is moving, the more violently that water is displaced. So, a mushrooming bullet that is moving faster will almost inevitably cause more damage than an otherwise identical, slower, non expanding round.
I feel like a pistol round becomes effective when it passes 1,000 for example, it needs a certain level of speed and energy to expand a bullet and poke a big hole.
A rifle round is different, bottle necked, long, heavy, narrow bullets, I feel that a standard rifle round needs about 2,000 fps to really expand and add anything to the wounding. Low velocity, non expanding rounds aren't even as good as being hit by an arrow. The .30 carbine or .38 special lead load are notorious for ineffectiveness. It left little holes like a screwdriver would leave. The typical deer broadhead cuts a bleeding channel through the tissues over an inch in diameter. No need for high velocity impact, good god, that thing rips a hole through a deer that can bleed it out in a matter of minutes in a good area.
Once you reach a certain threshold of velocity, construction, point of impact, the shock, or hammering effect can cause serious, serious damage. Look at a prairie dog or ground hog that was shot with a .22-250. That is all about high velocity hydrostatic shock. then, shoot the next one with a plain .44 magnum. You can dump an enormous amount of energy into a small area, or you can let it escape out the back door.