With the AR in 5.56 mm you get rifle caliber terminal effects without the over penetration issues you would have with your M1A or a shotgun loaded with #4 buckshot or larger or slugs or even with most handgun rounds. This is a known fact, despite a lot of internet buzz and unscientific youtube penetration tests.
Now I'm not saying that you won't see collateral damage if your home defense scenario looks like a shootout in a John Woo movie. But who is going to spray dozens to hundreds of rounds in a home defense scenario anyway? Sure the 5.56 rounds penetrate but they they usually fragment and lose enough energy that they aren't necessarily lethal. But then agian the idea is not to miss.
The downside is that you have to have some training to effectively move in a close environment like your home, but that applies to all long guns including a riot gun.
There are many things in home defense more important then your choice of firearm. When it comes down to choosing your "go to" weapon, pick the one that you shoot the best and handle the best. Don't worry about what is optimum. I can't think of a home defense situation where the gun the homeowner used made a difference in the outcome.
If you are using home defense as the only criteria for having the 6920 and you aren't comfortable using it in that role, then it is in fact surplus to you and you would be better served by selling it and investing the proceeds in training and practice ammunition for the weapon you do intend on using.
If you aren't confident or happy with the AR for whatever reason, I doubt that anyone here is going to convince you that you should keep it. It's all personal choice.
My 6920 is my "go to" in the house. Here's why:
1. It's the platform that I have the most experience with. I was issued my first M16 in December of 1974 and I have carried one in one form or another ever since. First as an Army Infantryman and then in my patrol car as a police officer. I have more formal training on that platform then any other. I've trained with Jim Crews, Pat Rogers 5 times and numerous LE tactical and patrol rifle courses. I can handle it better then any other firearm I own. I teach tactical and patrol rifle classes.
I've had plenty of handgun training and even shotgun training with the late Louis Awerbuck, but the AR is the weapon I have the most experience with.
2. I am confident in it's ability to stop a suspect and the M193 ammunition I use not to be a huge danger to anyone not in the house should I miss.
Those are my reasons for choosing the AR. Frankly if it wasn't the weapon I am most unconsciously competent with, I probably would have a different weapon as my "go to". But that doesn't mean I would recommend it to you or anyone else. I believe that one should choose the weapon he knows best for defensive use.
