Don't Misunderstand.
I'm not sure why so many shooters swear by the FBI standards? For a citizen you will not have a need to shoot through car doors or several of the other requirements the FBI test set.
Since when does a human heart sit 12" to 18" into their chest? Most will only need 6" to 8" to reach something important...
The FBI ballistics gelatin standard was reverse engineered from successful shootings. Cartridges which had proven satisfactory in collected shooting data were shot through the gel to obtain the minimum and maximum. The gel is not said by anyone to be of the same consistency as real tissue. "The standard exists to provide a uniform basis for comparison, not to provide any direct analogue to the human body."
The minimum standard is not hard to meet as has been explained here about hardball. However, a round which over penetrates will obviously not expend its extra energy in the target. A non-expanded 9mm punch through creates the same wound as a 380 punch through. OK fine, then use either one. No need for any testing. An expanding 9mm theoretically creates the same permanent wound cavity as 45 hardball if it also penetrates. If it does not penetrate then keep the .45.
A 45 ACP FMJ will travel through about 32 inches of ballistics gelatin, and the same round will completely pass through a bad guy about 50% of the time sometimes found captured by the skin of the back.
The inadequacy of the .38 Long Colt Revolver in the Moro Rebellion of 1899-1913 led to the ultimate development of the 45ACP and the 1911 pistol. It worked; it still works. The imagined failure of the 9mm Win Silvertip in the FBI 1986 Miami Shootout led to the ultimate development of the 40S&W. It worked, and it still works. The invention of the "bonded" 9mm hollow point is believed to also work, but as has been shown here on this thread there is still considerable doubt that the same thing can be said for the .380.
Current doctrine seems to me to be recoil control and mag capacity. Pour a lot of rounds into him really fast. You know like a 12 gauge shotgun does.
PLease correct me anyone, and I have enjoyed the thread Thanks!