Okay, I was wrong that DocGKR talked to that specifically, but here's a smattering of tests conducted with various .223/5.56 rounds against drywall.
Drywall Penetration Test - Landry Reloading Docs
Which Hornady TAP for HD?
Info on barriers and penetration • Shotgunworld.com
.223 Drywall Penetration: Ammunition
As you can see, the majority of the time the rounds are fragmenting by the time they reach the second wall. And most don't cause damage to the third wall. As compared with buckshot and pistol rounds, it's actually a better performer in the close quarters role, lack of over penetration specifically, than other rounds.
I completely agree with using a very light .223 bullet perhaps 40 grain Corbon or black hills or so. It's all location dependent. It's a great choice if you can get away with it.
Some folks can get away with using full on rifle rounds/ buck shot inside their houses. Others, trailers/apartments/tight subdivisions would need to stay with a min of #6-#8 shot. IMO
I've went out and shot several boxes of the same hollow point ammo into logs and other solid items, you'd be surprised at just how inconsistent the results were.
When it comes to shotguns. The only thing consistent about shotguns is just how Inconsistent they really are.
We know that over penetration isn't a problem, until it is. Then, it's a grand jury problem. Is it worth the chance? Well, it is life and death. So use the best possible.
Ever wonder why there is an ever expanding selection of hollow point rounds on the market? Always a new gee wiz round out there that is the king this week.
It's because most of these bullets don't do what they're supposed to do. Remember 85% of people shot with a hand gun survive. Personally, I think you can chalk that number up to people just not shooting that well.
At the end of the day, shot placement is and will always be king.
Very interesting reading though. Cheers