You do realize that most .223 rounds will not penetrate any further than a typical pistol slug right? This is especially true in the 45gr and below range.
Actually, lighter weight bullets from a .223 are SAFER for urban use than a pistol.
Here is an example:
55gr Horandy TAP LE Urban penetrates 7.5" with a max cavity of 3.5" after passing through wall board
http://www.hornadyle.com/products/ri...5-gr-tap-urban
135gr 9mm TAP Critical Duty penetrates 13.5" with a max cavity of 2" after passing through wall board
http://www.hornadyle.com/products/ha...5-gr-9mm-luger
Again, there are 45, 40 and 35gr bullets available that will show even greater decreases in penetration after passing through drywall.