What I have read, which may well be wrong, is that they chose the .223 because it was less likely to kill people. The idea is that a wound removes at least two people from action, while a dead soldier can be ignored during a battle.
The entire "chosen because its less likely to kill" thing is BULLCRAP. It's an armchair expert's assumption, based on the bean counter's defense of the light caliber weapon. They came up with the "wounded guy takes 2 or 3 guys out of action" as a justification that the small caliber round would not just still be military effective, but was actually better because you carried more rounds and each round could take 2 or 3 guys out of battle.
This idea is not 100% false, but its a long, long way from being 100% true.
The idea of a wounded solider, needing a medic and a couple of guys to carry the wounded guy/stretcher is valid, but one works in the real world when you are fighting people who place the same approximate value on their troops lives that we do.
When fighting Soviet/Chi-com type human wave attacks, and Asians with a cultural ethos of "death before dishonor", or anyone who isn't an organized military with a medical component in action, its a moot point.
We have, and are fighting people who mostly only treat their wounded AFTER the battle, IF they can.
When you're fighting a "civilized" war by the old European rules, and the other side is ALSO doing that, THEN the "wounding takes 2+ guys out of action" MAY apply. When you aren't, that "benefit" of the light caliber weapon is lost.
If this is true, then the .223 is a sorry choice for home defense, because a private citizen needs to incapacitate as quickly as possible. You need something that kills people fast.
this needs some correction, especially in terms used.
A private citizen does need to incapacitate an attacker as quickly as possible. BUT, they don't need "something that kills people fast".
BECAUSE, private citizens are NOT authorized to kill. Ever. This may seem like a minor point of language, but its not a minor point in the law.
A private citizen can be justified using deadly force to STOP an attacker. Not kill them. If they happen to die, as a result of being stopped, that's their tough luck. It's a quirk of our language, and the way the law interprets it, but it can have huge legal consequences if you use the "wrong" words.
You shoot to STOP the attack. Nothing else. If you say you only meant to wound, that is admitting you did not believe deadly force was justified, and that changes self defense into assault, at a minimum.
If you "shoot to kill" that changes justifiable self defense into premeditated murder. It may not be what you meant, but the law will take what you say at face value (THEIR face value) and charge you, accordingly.