Since all pistol rounds suck, what matters? Most of all, penetration.
Physiologically, no caliber or bullet is certain to incapacitate any individual unless the brain is hit. Psychologically, some individuals can be incapacitated by minor or small caliber wounds. Those individuals who are stimulated by fear, adrenaline, drugs, alcohol, and/or sheer will and survival determination may not be incapacitated even if mortally wounded.
The will to survive and to fight despite horrific damage to the body is commonplace on the battlefield, and on the street. Barring a hit to the brain, the only way to force incapacitation is to cause sufficient blood loss that the subject can no longer function, and that takes time. Even if the heart is instantly destroyed, there is sufficient oxygen in the brain to support full and complete voluntary action for 10-15 seconds.
Kinetic energy does not wound. Temporary cavity does not wound. The much discussed “shock” of bullet impact is a fable and “knock down” power is a myth. The critical element is penetration. The bullet must pass through the large, blood bearing organs and be of sufficient diameter to promote rapid bleeding. Penetration less than 12 inches is too little, and, in the words of two of the participants in the 1987 Wound Ballistics Workshop, “too little penetration will get you killed.” Given desirable and reliable penetration, the only way to increase bullet effectiveness is to increase the severity of the wound by increasing the size of hole made by the bullet. Any bullet which will not penetrate through vital organs from less than optimal angles is not acceptable. Of those that will penetrate, the edge is always with the bigger bullet.
So there you go. This is why calibers such as .25’s, .32’s, .380’s, and stuff like bird-shot aren’t considered ideal for self-defense, because they just can’t get down where they need to be. All pistol rounds suck, and some suck more than others.
Of course, the real important thing is accurate placement in the right spot because a deep wound in the foot doesn’t do much to stop your attacker. Must be accurate, then must penetrate, then the bigger you can make that hole the better such as with modern hollow-point ammo or just larger calibers (and cue the .45 is king flame fest!). 🙂
Note as well tho, this doesn’t just apply to handgun rounds and self-defense. When I go hunting, I need a toolset that will travel the distance and still have enough energy and ability to penetrate as deeply as necessary. Big game animals are man-sized or larger, with potentially tougher hides and structure. I won’t take a .22 LR deer hunting in the Texas Hill Country, but my 6.8 SPC with Barnes TSX bullets can do the job just fine. So can .308 Winchester, so can a lot of other proper rifle calibers. But on the flip side, you still have to worry about over-penetration or being too much for the job. Oh sure, I could hunt a deer with a .50 BMG but I’d ruin lots of meat and that bullet would keep travelling right through the deer and come to rest who knows where. That too could have lots of problems. Firearms are more specific in their application than people tend to believe, so make sure you choose the right tool.
Bottom line: consider the intent behind the tool and ensure to use the proper tool for the job at hand.