working inside a house, working cover, etc, a small package is a greater advantage than power. Besides, if were still talking indoors CQC, people pretty much drop with not a lot of persuasion. You don't need an elephant gun. even three .380 in the right places is enough to take the fight out. If you want to be dead sure you have knock down then .45ACP is your best and its sub sonic. Ive heard one shot from a 1911with a can indoors at close range without muffs and it was like a phonebook drop. thud...
My idaal indoors gun is a Kriss Vector .45 with a can.
The RDB survival has become hands down my favorite gun and the one I keep with me in my truck and shoot the the most. Yep, it needs a little tinkering on the gas system, yes you need to properly loctite everything, no I wouldn’t take it if I knew I was going into battle, but dang, the thing is so compact and fun. I also have the 20” Hunter model which I cut down to 18”, also a fun and reliable gun, although significantly heavier.
Edit: I think it would be a reasonable self defense option, although I probably wouldn’t opt for the 20” version, at 16” barrel length and home defense distances you will have no issue with velocity or bullet performance. Personally I feel more comfortable with a handgun for home defense.