230 grain 45 FMJ's have about 25 inches (65cm) of penetration in ballistic gelatin. 9mm Luger FMJ is about the same, by the way. Does anyone have any data on lighter weight FMJ's?
But the thing is, something like 80% of shots fired by police miss anyway, so if an over penetrating round is your concern, the logically you would determine that firing
anything is too dangerous! I don't understand why this is so rarely brought up. In addition, unless you're on a train, the chances of you hitting a bystander are so small versus the certainty you or someone else are going to be killed or maimed, that I say fears of over penetration are exaggerated.
I thought that because of the felony murder rule (or something else), that anyone killed during a crime is the liability of the person committing the crime, even if they don't do the actual killing. For instance, in various Armed Citizen columns, I've read of a pair or criminals attempting to mug someone, who shoots and kills one bad guy, and the surviving one is charged with murder. But I'm sure this varies state to state.
Anyway, FMJ's are cheap, and since shot placement is more important than the bullet, and if ammo cost is a constraining factor, I think practicing a lot more with and carrying FMJ's would be a good idea.