There's a show on Verizons programming called Best Defense. Its a VERY good show (I dvr the series). Covers all forms of self defense: home, parking lots, malls, ATMs, etc. Anyways, they did one show, using several 2x4 walls several feet apart (on an outdoor range) and fired a 9mm jhp, 45 jhp, 223 rifle, and 12 ga using 00 buck, then birdshot- demonstrating 1: if you were to miss your "threat", and 2: how the rounds reacted to the drywall(s), and how far they travelled. The 9mm went through all 4 sets of walls, as did the 223; the 45 stopped at the 4th wall, 00 stopped at the 3rd wall, and birdshot barely made it through the 2nd wall, illustrating that your child or your spouse hiding in another bedroom could very well have been hit or killed even down the hallway! So, for the home, shotgun would be the preferred weapon, other than that, even though the 45 is a bigger more powerful round, there is much less chance of the round going through your target and into an innocent victim, due to its lower velocity. If anyone has Verizon with the DVR, search Best Defense