All that crap looks great in a movie with plenty of costumes and special effects, but a 12" sawed off (essentially an Auto and Burglar Gun) is almost worthless. They kick hard, they are deafening loud, and they are fire-breathers, which all serve to discourage anyone from using them and therefore reduce their efficacy.
And besides, isn't this a TEOTWAWKI thread, and aren't they "non grata"?