Plus, remember, the family (lawyer) of the bad guy you dispatch with a SBR or FA firearm, will have a field day making you some kind of Bible clinging, Right wing militia member hell bent on killing someone.
(Even if they kick in your door for a home invasion won't matter)....
Get a .45 and a 12 guage. same result, and easier to defend. A standard AR, with frangible ammo will even work for SD.
Also, what state are you in? Texas works, CT, MD, CA, NY, probably won't....