I own am M1A but my 12 gauge is what I keep closest to me in my bedroom loaded with 3" 00 buck. That way I don't have to worry so much about my aim and I don't have to worry about my bullet going through a tree, into my neighbor's house or traveling a half mile and killing someone. To each his own though.
Respectfully, I have a colleague who was a police sergeant for many years. He related a story to me where some fella robbed a bank, and the cops were on him. He started to run across a field, and turned to fire on the cops. One of them dropped him with a shotgun and 00 buck. He was DRT, still clutching the bag 'o money with one hand and his pistol in the other.
One of the pellets from the shotgun traversed the field, penetrated the side of a lady's house, pierced the side of her refrigerator and lodged inside. The cops replaced the fridge and repaired the damage to the walls.
Based on this first hand account, I can tell you that I will not be using 00 buck, if one of my considerations is over penetration.
Too I respectfully disagree with the aiming comment, as one must aim a shotgun at any sort of home defense distances if one expects to hit the target.
Which would you get for defensive situations? Just to make it equal in terms of price and quality, I'm talking about the $1000 PTR-91 vs the $1000 Arsenal AKs.
While the range and accuracy of the PTR will tend to outshine the Kalashnikov, I find it hard to conceive of a situation where I could keep a straight face describing to a jury a "defense" situation where the distances were any more than 20 yards. Perhaps such a situation exists, but it is difficult for me to conceive of.
The real danger of over penetration applies to both of the cartridges fired by the PTR91 and the Kalashnikov. If I were to purchase either of them, I would definitely want to do some penetration testing and water jug testing to see how it performs before putting it into a HD role. I'd hate like hell to shoot a BG, and kill the neighbor kid asleep in her crib as the round went whistling on through walls and such.
Just my $.02