SBR AR-15 If you truly need to protect yourself 30rds of 223 in a tactical platform is hard to beat ! the bigger choice may be ammo. My house is old enough that it has Plastered walls. I doubt that a hollow point will consistently enough go through a wall to get at an assailant using a wall for cover but a fmj may zip right through a person (or Zombie) not subduing them as fast as a hp will.
BTW I have a 45xd with Trijicons in a small safe by my pillow (16''away) HOPEFULLY this will keep me & my family alive until I can get to one of my ARs.
I have small children so I don't have the option of being able to have a just gun laying out...