You're assuming that accurate, aimed fire cannot be accomplished with a semi auto rifle.
Not at all. How did you manage to conclude that from what I wrote? Where was it implied or stated?
Furthermore, you're presuming that just because a cartridge has good ballistics that it is automatically more deadly at range.
Yes, I am presuming that a larger more powerful full size rifle cartridge is, with an accurate shooter, more "deadly" at range in compared to a smaller, less powerful mid range cartridge. Yes, I think that is a pretty safe presumption.
You're completely ignoring the platform the weapon is being launched from (old, iron-sighted, built using construction techniques that aren't as good as modern CNC machining.)
Construction techniques that aren't as good as modern CNC machining? Are you saying a aluminum AR is superior to a Swiss K31 in terms of construction quality?
At those distances, at best, you're engaging in harassing fire, which was probably a cool thing back in the days of pith helmets, monocles, and volley sights, but doesn't work so well nowadays, which probably explains why the people we're fighting much prefer to use IEDs to engaging in actual firefights.
They use IED's because they have dated weapons, less trained personnel, and virtually no air power (the real kicker). And so IED's are an efficient and demoralizing way of fighting a war that they otherwise would not have a chance at winning.
As for harassing fire, it is harassing fire nonetheless and it has been widely reported and the military is attempting to act on it by obtaining more DM style full power rifle cartridge weapons.
If so, then why is it the overwhelming choice for so many police, military, and competitive shooters based on Stoner's design?
It's akin to saying the Mossberg 500 is the end all in shotgun home defense because there are more people who have them than other shotguns or that the Remington 700 is the last word in bolt rifle design. Just because it is among the most popular doesn't mean that there aren't other valid designs that have been or are being used.
There are plenty of excellent auto loaders to choose from. The AR is just one among many.
Superior ballistics become something of a moot point if the bullet is being launched from a platform that is sub-optimal, or being employed by a shooter with sub-par skill.
And as I stated at least three times in this thread already, my references were to a skilled rifleman not an untrained hack. I guess that went unnoticed.