The FBI has studied shock against humans. There is more hard data on what kills humans than there is about animals, which latter is mostly anecdotal. The FBI concluded that any bullet which meets their penetration test, whether 9mm, .40, or .45 ACP, kills by loss of blood only unless the CNS is hit. Therefore it does not matter whether you shoot a 9mm or a .45 ACP, provided you use the proper bullets. However they also concluded that shock is a factor against humans if the bullet impacts at more than 2000 fps.
The FBI has NOT in fact studied "shock" against humans. I have no idea where that idea may have come from, but the FBI is not a medical/physiological research organization.
Furthermore, the "FBI" standards for bullet performance are not even the FBI's. The gelatin performance standards were decided upon by a committee of experts, which included highly respected ballisticians like Dr. Martin Fackler, in 1987. It was Dr. Fackler's research that primarily led to the adoption of the 12-14" penetration standard for handgun bullets, and the FBI was given the charge of testing ammunition for the good of the law enforcement community (and since then, the non-LE self-defense shooting community).
Since then, there have been a lot of data accumulated by various agencies on the actual performance of service caliber handguns and ammunition. These databases basically support the idea that rounds that meet the "FBI" gelatin standard perform well in actual shootings. But no one has actually done any laboratory studies of the effects of bullets on live human beings, which would be needed to "study shock against humans"; in fact, it's almost impossible to get ethics approval to do any ballistics testing against animals. So let's not perpetuate that myth, shall we?
As for the "2000 fps" threshold you mention... I'd like to know where you got that figure. Fackler, McPherson, and other ballistics researchers have noted that bullets with velocities greater than roughly 1000 m/s (about 3240 fps) seem to have greater destructive capacity than bullets travelling slower than that, but this has never actually been quantified. It's really just an opinion, and one which I happen to share. But it's hardly "proven", scientifically speaking. In any case, 2000 fps is not a threshold I've read anywhere in the terminal ballistics literature.
