My problem with the AR for home defense is pass through capability with the ammo. A shotgun and buckshot to me is safer for the innocent neighbors. You can doll a shotgun up as well as an AR. The squirrels may have known the old man had one and more. Glad he got the job done. We all have our druthers.
Mobility, recoil management and capacity are unacceptable with shotguns...
The mobile home where the shooting occurred is on a 20-acre lot with dense woods and a single-lane dirt driveway. The distance from a gate to home is roughly 300 yards.
Your understanding of overpenetration risk, vis a vis buckshot and .223, is exactly backwards. Much testing has been done, the results are clear.
Like everything, it all depends. FMJ drywall penetration is always a concern, but personal defense ammunition is designed with this in mind. The majority of police cruisers in the US probably have an AR in the trunk and most are probably loaded with personal defense ammunition. The police are concerned with whatever might be on the other side of a wall, too. (When considering the purchase of a tool, I look to what the "experts" in the field choose.)
There are multiple tests of ammo versus drywall available online and on YouTube. Buckshot penetrates drywall very well.
Studies have shown the exact opposite to be true. "Over-penetration" is a greater risk with .00 buckshot, 9mm or .45ACP than with a 5.56.
Article with multiple test results here
There is a reason dynamic-entry professionals prefer the AR-15 when there is a risk of one of their own being behind a wall or doorway.
Bottom line is the AR-15 is the ideal weapon for home defense. Light, small, easy to wield by men and women alike. Easy to aim. Very lethal. Lower over-penetration risk than conventional home defense firearms.
The OneStrike frangible jacketed ammo seems very promising. Looks like it gives about six inches of penetration, dumps all of its energy into the target and makes a real mess.
Well, you’d be rather technically wrong in your position. Even 55 or 62 FMJs will and do fragment at conversational distances even through simple sheet rock/frame construction. 33 cal lead alloy balls do not. There s so much good testing info on the net I’ll let you look it up. But in summary, a high velocity 224 diameter bullet ( there are better than fMJs out there too) does wonderfully horrible things to what it connects with, but unlike malleable lead alloy buck ( maybe #4Bs would be best), is much less likely to penetrate excessively.
Anyways, whatever you use, guard yourself and yours well!
20 acre lot, no other occupants of the residence, etc. The AR with its larger magazine capacity was the right choice for that location.