Jim243, don't use frangible ammo for self-defense. Frangible .223 ammo is designed to fall apart when it hits a hard surface, but it doesn't always work as well when it hits a softer surface like drywall or the human body.
If you want maximum fragmentation with excellent effectiveness, go with V-Max ballistic-tipped hollow points. These will start to fragment the moment they hit anything. You'll still have enough velocity to penetrate in the body, but these rounds will penetrate through walls less than almost any handgun or even shotgun load. I like 55 gr. V-Max .223 for my home-defense AR.
0331: "Accuracy by volume."