I agree with a few posters, a 12-gauge pump shotgun with 18” barrel is the perfect home defense gun. Discharging ANY weapon inside a house is going to be loud so I don’t buy that arguement there.
Don’t get me wrong, I have a .45acp I use for carry and HD as well but one has to be more precise with a .45acp round as opposed to a shotgun. A properly setup HD shotgun (instant-on light, 8+ round magazine, tritum sights) will be better in almost any situation. A pistol is handy for ‘clearing’ around walls and doors and should be on your hip as backup.
A Mini14/AR15 in a home? No F’in way, even with frangible bullets! Even 9mm and .45acp rounds will be a problem if you miss your target as a bullet will go through several walls before stopping. 00 and 000 shot will not penetrate through multiple walls yet all energy will be absorbed by an immediate target.
Careful with the assumption about penetration. Here’s an interesting site with some experimets (and funny comments about the effect of racking the shotgun)
http://www.theboxotruth.com/docs/bot3.htm
12 inch or so would be even better.. if not for that stupid federal law. You would lose magazine capacity in a standard tubular magazine, but there are some with box type magazines.