Not hobby related so I've moved this to the litter box.
Always know your target and what is beyond it. Also, there's potentially a lawyer or a jury attached to every bullet you fire no matter where it lands.
Any round sufficiently powerful to penetrate the 12-15" needed for vital organ damage (standard recommended by the FBI) will also easily penetrate many Sheetrock walls.
Check out box-of-truth for a large number of ballistics testing on Sheetrock walls and other obstacles using a wide variety of calibers. Here's one where he fires a variety of rounds including .223, 7.62, and those silly Glazer 9mm rounds: http://www.theboxotruth.com/the-box-...e-box-o-truth/
Contrary to popular belief, the .223/5.56mm round is perfectly suitable for home defense when compared to pistol calibers and shotgun buckshot. It's a myth that it will significantly over penetrate simply because it is fired from a rifle at much higher velocities. Ballistics test after ballistics test just shows that not to be true. Google ".223 penetration testing" for more info. Watch this for a comparison of 9mm, buckshot, and 5.56mm against 7 interior sheetrock walls: https://www.youtube.com/watch?v=AXOIQgfvVlE
If you're deciding between an AR-15 platform chambered in 5.56mmx45mm vs an AK in 7.62mmx39mm there is no question that the 7.62 round has significantly more power and penetration. Personally, if over penetration is at all a concern that removes 7.62mm from consideration.
Good luck...