It first caught my eye when I was watching a show on TV where they were doing some close up training drills using steel targets. When I say close, I mean like two yards from a steel silhouette. As I was thinking about ricochets, a guy on the show asked the same question.
They started talking about Frangible Ammo.
The guy actually walked up to the target to about 3 feet and fired.
Frangible Ammo does more than expand on impact, it completely fragments, some types even turn to dust. The Frangible Ammo was specifically designed to prevent over perpetration through walls more than a training tool for shooters. Ballistic Jell tests really show that you do NOT want to get shot with these. They shred totally on impact. Two layers of drywall is cover!
--Got to get some to try!