Birdshot for home defense? Really? I need to take a spoonful of salt while listening now.
if you shoot a in a defensive situation the distances would not be that large at a guess 5 to 10 meters at most maybe a little more, normally less than 10 though depending on size of the room
now the Patton from a shot gun at those distances would still be quite tight even with open chokes
in that case bird shot would be quite an effective shot to use and due to needing to know your back stop if it was to go though gyprock walls you need to know that it won't go far and where it is going to go.
I have seen my self while hunting when Old Mate missed a fox and 1 pellet ended up cracking a side windscreen and mirror on a CAT Front-end loader all because 1 pellet went over a 20 foot sand pile in a Quarry
he had to pay for a new mirror and screen