Don't tell me that rifle bullets don't go though walls.
Handgun bullets go through walls better than properly selected rifle bullets. Ball ammunition (.30-06) from my '03A3 (poor choice) will go through my house, my neighbors house and probably into his neighbor's house.
All bullets are not the same. If I were going to keep a loaded 5.56/.223 rifle around for SD/HD, a fairly frangible load (as illustrated in the link) absolutely does not penetrate as much. The reason is the high velocity combined with short range. This test barely got 6 inches of penetration at 200 yards, at close range, probably even more fragmentation.