Steve-
I am an NRA HighMaster in highpower, but a new member here. There are two divisions in NRA HighPower, Service Rifle and Match Rifle. In service Rifle, which I shoot, you have a choice of three rifles, M16/AR15, M14/M1A, and the Garand. (The Springfield IS NOT a legal rifle in the Service Rifle Division).
Match rifle shooters are limited by only caliber, .30 or less.
I don't know where that one fellow shoots, or his experience level, but the bolt gun still rules the roost in match rifles. Some people do shoot ar15 based "spaceguns", but the top level shooters almost uniformly shoot a boltgun of one flavor or another. The hottest, cutting edge match rifle is a Tubb2K, made by McMIllan, and it is a bolt gun.
Some people have gone to great length and expense to have a match rifle made from an AR10 or SR25 platform, but those match rifles are not common, nor have they proven reliable.
The accuracy issue is not the determining factor here. Actually, most NRA HP rifles consistently shoot 1/2 MOA, and it is cheaper and easier to get an AR to be 1/2 MOA rifle than a bolt gun. The reason that the bolt gun is the predominant choice in the Match Rifle division is actually because of 2 factors, caliber and lock time/ trigger.
Bolt guns can handle more powerful, better wind bucking calibers than the AR platform. Current favorites in NRA HP are 6XC, 6/250, 260 Rem, 6BR. These calibers, shooting a high BC bullet at a decent velocity, make a difference for an able, experienced shooter, particularly at 600 yards.
Lock time is also an issue for NRA HP shooters above a certain skill level. While I love my AR's, its lock time is like molasses compared to my Tubb2K, or any of my Remingtons, Winchesters, and other HP boltguns I have. The trigger is part of this issue also. The best trigger in the Match Rifle division for an AR based space gun is either a Knight's or a Jewel. They can be adjusted down fairly lightly, but no matter what you do, they don't compare to a top flight trigger like an Anschutz in a boltgun.