Oh dear. Get thee to the range.
Yes, the M16, M4, AR15, etc, etc are chambered in .223.
The military likes .223 because it is light and troops can carry *lots* of ammo. It is not considered a sporting cartridge for whitetail deer. This should tell you something about this "high power" round.
Much of the western word prefers 7.62 NATO aka .308 in Amerispeak. 308 is an excellent sniping round and battle rifle round but the bullet alone weighs more than the entire round of .223.
Everything you ever wanted to know about .223.
An excerpt from:
http://www.snipercentral.com/caliber.htm
5.56x45mm NATO (.223 Rem)
The .223 is used for law enforcement applications, largely because some agencies fear the over penetration of the .308 round in hostage type situations. The .223 generally splinters on impact, allowing almost no excess penetration that could possibly hit innocents, such as hostages. But with this fragmentation and lack of penetration comes a necessity for more precise shot placement, leaving almost no room for error. The .223 has a small temporary wound channel (Stretch cavity), requiring almost a direct hit on the spinal stem in order to get "lights out" on a target. The lighter .223 bullet, with its low ballistic coeffecient, is very susceptible to the effects of wind, which really limits its long range potential. While it is possible to achieve acceptable accuracy at 600 meters on a calm day, it is too risky on the windy days to really consider this round for military sniping purposes. Due to the lack of penetration and lack of energy, the .223 should only be used in very rare circumstances and only on head shots. There is more then one instance when a target has been shot with a perfectly placed center mass shot, and it failed to incapacitate the target. The very heavy .223 bullets (75gr +) are becoming more popular in long range shooting, but the special barrels and rifles required to shoot these high BC bullets are not available as standard sniper rifles to everyday snipers.
Note: In order to stabilize the 69-gr. Bullets and heavier, the twist on the rifle barrel needs to be at least 1:8"
Recommendation: only use the .223 within 100 meters and only take head shots if at all possible. If the .223 is all that your unit has in the way of a sniper rifle, be sure to keep in mind the limitations of the round.
Yes, all the NATO countries, except France, use the 5.56X54 for their service rifles.
However, Savage, Remington, New England Arms, Ruger and a few others manufacture excellent bolt-action or single shot rifles in this caliber.
The media in it's effort to help the anti-gun crowd is broadcasting the AR-15 or the Mini-14 as the likely rifle for this.
I cannot help but wonder why this idiot has only taken 1 shot, and not a number of shots. If he is using the AR or the Mini, he certainly has a number of rounds available. If this is the cas and it is a bolt or single-shot, the police are going to have a HUGE plate of crow to eat.
Oh, and one other thought. I was interviewed by a local TV station for an opinion about "ballistic profiling" that has come up around this sniper story. One of my comments was to the effect....."If someone with a licensed CCW were around at the time they might have been able to stop this guy, but that whole area of the country has outlawed personal protection. Go figure." This comment didn't make the broadcast.