If you're worried about gangs of bad guys, maybe you should look into an AR15 for HD. Same goes for if you think they would be wearing armor.
That said, when the shots start getting fired, many BG's flee ASAP. That doesn't mean that they won't shoot back. I am just saying that you won't likely come across a gang of BG's that will sit there and fight it out to the last man. BG's tend to prefer easy pickens and a shotgun wielding homeowner is not likely to fit that description.