Maybe my googlefu is bad, but I have not been able to find any documented cases of overpenetration. Though there have been cases of missed targets causing injuries.

As far as how effective a round is, Michael Brown really disproved the notion that HP stop bad guys. MB was stopped finally after he was shot in the HEAD. From what evidence, and testimony that has been gathered MB was still advancing up until the head shot. IIRC this was with police .40 S&W hollowpoints shot from a Sig.

So what I get, as if it mattered because it doesn't, is that chances of a overpenetration bystander is very low, extremely low. But that HP are no guarantee of a stop, that in many cases it takes a head shot to stop the threat. That does not matter if it is a HP, or a solid. I would put my odds on the solid to smash effectively through the skull.

I say as if it mattered, because it doesn't because we all make decisions base on our own factors, not others factors. I am going to carry what I carry not based on others opinions. I also am not going to change anyone else opinion on what they carry. That is as likely as a everpenetrated injury.

I carry exclusively HP for HD/SD in my handguns. I usually settle on something that has been thoroughly tested by those with access to large numbers of "street results". Dr Gary Roberts, et al. Those guys seem to believe there is an advantage to a well designed HP over a solid.

With handguns, the permanent wound cavity is what matters most (to include accuracy). Those wound channels tend to be nearly double the size of a FMJ when a modern design HP is used.

There is no magic handgun bullet, certainly. Why wouldn't I increase my odds as much as possible? When I can buy top of the line HP ammo for $25 per 50, it is an easy choice for me.

YMMV.

I carry ball in my .45 only when I visit the People's republic of New Jersey. Otherwise hollow points in everything.

Yeah, I confess. Ball only in my 1967 Baby Browning, Beretta 70 .32 ACP and PPK .380. Ball 95% of the time in any of various 9mm's, and ball almost exclusively in .45 ACP's. The rest of the time it is 200 gr. SWC's at about 950 fps. That's mostly because ball always works in my guns - always. And that's what has to come first in a defensive handgun, always. Next, in my mind, comes penetration. Hollow point doesn't help if it doesn't get where it needs to be. Ball gets there. You know the old saying "They all fall to ball."

"I think some of it has to do with my life's work of standing over dead people and trying to find out who made them be dead."

Bhaaaaa you gotta with words

IIRC twelve shots fired. First at contact range in scuffle over gun, slightly injuring assailants hand. OUT OF NEXT 11 THERE ARE SIX MISSES AT A DISTANCE OF ONLY A FEW FEET. Shot 12 was instantly fatal going through top of skull. I will say that #11 went throgh the eye socket, preciptating the lunge/fall. SO OF THE MIDDLE 9 SHOTS AT CLOSE RANE 2/3 MISSED. Those that hit hit arm twice and torso. They did not stop the assailant.
1. As realtors say Location Location Location. 2. No magic bullets, particuarly for arm shots. 3. Wasting time reaching for that tazer can get you killed.

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Certified Curmudgeon