I'll never understand why anyone would want more than a handgun or shotgun for self-defense. My uncle was a sniper in WW2 (yeah he was old) he use to always say "if you can't kill someone in one shot you have no reason to own a gun." This is how I was raised too. So 30 round mags are funny to me. Auto's are fun as shit though. I understand why people like them. Being a SAW gunner in the Army was always fun because if you're good enough you could pop one round off and hit your target. I use to do that all the time and piss off my NCO's.
There was a home invasion in Stockton recently that made the news. 4 criminals pulled up to the individual's house, each armed with a rifle (some were full auto, some where semi).
The homeowner was lucky enough to see them approaching his house via his security cameras, and managed to properly defend himself using his AR15 before they managed to get to his door.
A handgun's inaccuracy at those distances would have posed a much greater risk to bystanders, and a shotgun would have been just as difficult to aim (00 buckshot would have an undesirable spread pattern, and a slug at that distance would be very difficult to aim even with ghost rings).
This whole ordeal was actually caught on tape. I can try to find it, although it happened a year or two go.
These sort of situations aren't that rare. We were given lots of local data during my CCW course.