Comparing the 223 to the 6.5s (popular long range round) assuming you have the twist to use heavy bullets in both, you only have about a 2 MOA wind difference at 1000 yards.
Problem is a 3 MPH wind error at 1000 yards gives you about the same 2 MOA difference in drift.
How may of us can tell the difference between a 10 mph wind and a 13 mph wind 1000 yards down range.
The thing is, in 1000 yard rifle matches you have three categories (meaning you normally shoot three matches (individual, excluding team matches)).
You have the Any Rifle Any Sight, Any Rifle Iron Sights, and Service Rifle.
The 6.5s work in the first two, but they don't come in a service rifle configuration.
But service rifle matches are limited to the 223s and 308s so you have to compare the 223 to the 308. The 223 has about 1/2 MOA less drift then the 308.
Sure there are better bullets and rounds then the 223, but not in the Service Rifle.
The 7.62x39 or the 5.54 Russian rounds certainly cant compete with the 223 at distance.
The problem is the barrel twist for the 223s, Our service rifles have a 1:7 twist and they will handle the heavy 223 bullets, Many of our civilian ARs don't, that is where people are having problems at extended range.
Its not the round its the twist we choose for our ARs.
I don't see either the 223 or 308 being "under rated", sales figures dispute that.
Nor are they over rated for a long range round.
Get the proper twist, get some heavy match bullets and most important, regardless of what you shoot LEARN TO READ WIND AND MIRAGE.
That is the caveat.
I don't mean take your Krystol, stand at the firing line and get a reading. What your Krystal says at 6 ft off the ground and what the wind is doing at max ordinate is as different as night and day.
The Max ordinate of the rounds listed above is somewhere between 25-30 feet. Next time you go to a range with range flag go to the mid range flag pole. Put a flag at the top, about 30 feet off the ground, then put another flag about 6 foot off the ground.
You'll notice the flags, standing out do to wind, are as different as night and day, they may even be blowing in different directions.
So in reality, as I harp on quite a bit, its the shooter, not the round, not the rifle.
CPT USAR Ret
USAMU Sniper School Oct '78
Distinguished Rifle Badge 1071