Is this different form the .223 Remington that's been around since the 60s?
I've also heard it was designed to wound, but that conflicts with the "devistating" tumbling characteristics it had when under rifled. (1:12 in the original, now usually between 1:9 or 1:7, so that effect is gone)
It was also designed for it's light weight, flat trajectory, and lack of recoil. Most of this was our military switching to full auto assult rifle from the .30 cal battle rifles (M1, M14). Basically, easier to shoot full auto, and you can cary more ammo for spray and pray. It was a McNamara thing, so who knows what the decisions were based on.
I love my AR-15, but would much rather our guys had M-14s or AR-10s in combat.
No except as to details of bullet design and sometimes powder used. 5.56 NATO, which is what the military calls it, was evolved from the .222 and so Remington, who did the evolving, calls it the .223. The AR-15/M-16 was first introduced into the military (The Air Force, IIRC) in the early 60s, there are pictures of JFK firing one, although it didn't become widely issued until a bit later.