No expert here; you may want to check out Paul Harrell on youtube; he's very informational, and has many videos on penetration. Most homes, and cars offer little protection from modern ammo; an .223/5.56 can penetrate; so can a shotgun slug.

Bird shot for defense can be underrated; sometimes.

I guess the only other things I can think of that would be important for you to keep in mind for defense, home, or away. No matter how justified in the shooting you are, you will be sued civilly. You'll need a balloon policy of $1 million, or better.

You've got to comprehend insurance carriers, and lawyers. Lawyers will take any case they can find money on. When it comes to homicide; which is what you'll be committing, even if it's proven to be self defense, will still carry the title, 'homicide', uninformed juries eat this up; most juries are uninformed anymore. Any ways, short of a million balloon policy, the insurers will pay out, even at that, or above, the plaintiffs can still draw it out in court, and cost money; meaning a claim, and payment at times.

If you don't have enough insurance, you'll lose your butt; if you actually committed a negligent homicide in any way, often times your insurance company will walk away; as they don't insure crimes.

So on that note, study up on carry incidents, as well as at home incidents; learn what you can, and cannot do. You're more than likely going to be arrested, whether in the right, or wrong; be ready for that, and what to say, or not to say to the police. They maybe your biggest help, and your biggest enemy.

Aside from that, on load up, and what guns; those matter as well in the eyes of an ignorant jury. Someone 'alternating' their rounds, is easily seen as someone who maybe engaged in criminal activity; no shit. Likewise, carrying FMJ's, and/or other ammunition can 'label' you in the eyes of the law; even when you should be in the right.

My biggest advice? If you're really not scared for your life, and have something to lose, then lose it willingly; if you feel your life is in imminent danger, and you feel so strongly that you care not what happens next, as long as you get to take another breath, don't hesitate with your actions. Let the rest work itself out, and PRACTICE!