For the Army, the Navy, and the Air Force, this is most likely true... For the Marine Corps, however, it's a different breed altogether.
For starters, every Marine is a rifleman - from the mess hall attendant to the scout sniper. I didn't serve in Vietnam, as I wasn't even born yet, but I did serve 8 years on active duty from 1996-2004. During those 8 years, every Marine was required to qualify with the M16 A2 service rifle on a KD range with the last qualification period on the 500 yard line with open sights...yeah, 500 yards with open sights. I'm pretty sure nothing has changed since, with the exception of the improved GI service rifles.
That last sentence of the article is total BS... I can put 10 rounds in the black on a "B" Modified Target at 500 rounds with the M16 A2...open sights - and so can 80% of the Marines I served with.
I'd be happy to duel it out with ANY goofball and a flintlock rifle against my M16 A2, anytime and anywhere...
Well, I'm not about to dispute what the Marines do, but at the end of the day, I'm not a Marine. Nor Army/Navy/Airforce, for that matter. So, if I'm ever in a firefight, odds are, not only will I more than likely be by myself or maybe with one or two others, I won't have any backup, artillery support or a medivac to whisk me away to a field hospital. In short, what works for the military, and the Marines, may not work all that well for me. In that regard, and as Boston T. Party says several times in his
Boston's Gun Bible, 5.56/.223 really shouldn't be the caliber of choice.
And while I do not question your ability to get shots on target at 500 yds with an M16 A2, the effectiveness of that round at that range is simply not something I would feel all that comfortable with. Granted, while I obviously wouldn't want to take one to the head at that range, even the least bit of cover repels the round. For example, I recall several years ago shooting out to ~600 yds with a friend of mine. We were shooting at newly painted iron gong; I with my .308 and he with his .223. And while I would say that the .223 may have been more accurate than my .308, when I hit the gong, it moved, made a solid report and left a mark we could easily see with our spotting scope. Not so much for the .223; other than hearing an ever-so-slight report, the gong didn't move nor were there any visible markings from the impact. I'll just leave it at that.
That being said, don't get me wrong... I've got several rifles chambered in .223 and enjoy them a lot. One of them is an HBAR AR in A2 configuration. First time I used it in a CMP match, got the silver medal below.