I can kinda see where the OP is coming from, however, the use of an assault weapon that fires centerfire rifle rounds, indoors, in a suburban area, during a time of national peace, seems like a bad idea.
Its dark, maybe pitch black. You have more than likely just woken up, your going to be confused, disoriented, and your awareness is going to be impaired. Your aggressor is completley alert, possibly already in the house, possibly hiding if he knows your awake, and possibly under the influence of some mind addling drug.
I know from experience that if you were to get in the situation where you get surprised and are in a melee confrontation with your aggressor, it is going to be MUCH easier to control and keep and handgun than a rifle.
Im not saying a trained person could not effectivly control and utilize their assault rifle in the above situation, although I am saying such a trained person would have an easier time with a pistol.
My biggest issue with it by far though is overpenetration, especially if using FMJ rounds.
I am not at all opposed to the use of a security shotgun, especially one with pistol grips that would make it more manueverable and easier to control (until you shot it that is
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Shotguns are often used as home defense weapons, bring more than enough firepower and intimidation (which this thread seems to be based on) to the table, and have a much lower chance of accidently shooting out your neighbors window. Plus, in the unfortunate event of a shooting, I doubt the legal percussions would be any different than using a handgun.
Personally, I would feel the best equipped with a handgun 9mm and up that holds at least 15 rounds. Or any revolver under 6" .357 and up. But thats because I am a wheelgun guy.
I can honestly say though, that for home defense purposes, Im not a fan of .380 or anything smaller, and I also would not be trying to play hero with one, though I don't see anything wrong with it strictly for personal defense.