When you shoot in a match that only 308 is allowed for what 30yrs it's pretty simple to say 308 is the most accurate.
I could see NRA going to the 308 for those matches since other countries have a say on what's being used. When the 30-06 was dropped if it was only for accuracy why didn't the retest the classification system given using the 30-06. Same when they changed target size.
NRA is a score shoot also classification system but it's not perfect in that once you get to High Master you never have to shoot to that level again. Maybe that's one reason they never retested.
Besides winning they give classification awards
http://competitions.nra.org/document...f/cp500-13.pdf