Last night on the TV, Self Defense TV, was a penetration test using 3 in line residential wall simulations on which would pass through certain rounds.
Two layers of sheet rock board on 2X4 farmes were fired at using 1) Bird Shot 2) .00 Buckshot and 3) A slug. No insulation material between the frames.
The test revealed that bird shot does just fine with dimples on the
2nd wall with a 3" dia hole in the first wall....not bad at 10 feet. The .00 passed through first wall and 50% exited through 2nd "wall"
The slug pentrated all three with ease. The conclusion by the TV hosts was for in home SD, Bird shot is a pretty good choice if collateral damges is a fear.