An AR-15 is not "home defense" unless you want all your neighbors ducking bullets that come through the siding and sheet rock. You could shoot through several homes with an AR, with an AK-47 you can shoot through cement cinder blocks!
Even a strong handgun could fire through several homes or apartments like a .40 and especially a .357, you could fire into the parking lot or driveway without leaving the living room.
home defense get a 12 gauge with some good 00 buckshot, it will make huge holes close distance and its range is limited to about 50 yards (if that)
if you still want to reach out just buy rifled slugs and keep them in a sidesaddle on the shotgun when and (if) you ever need them, I can hit a target around the distance of a football field with my remington 870
this guy is alot better than me so it is possible at 200 yards and its with a smoothbore
http://www.youtube.com/watch?v=ksDWE...eature=related