Do you mean the fact that the military rifles use the Rem. 700 action? It is a wide spread and easy to use action. Also it has a lot of adaptability with multiple stocks, barrels, and other aftermarket parts. Still there are rifles such as the Blaser LRS2 with a great action that is new that only involves the shooter in pulling straight back instead of up back forward then down. Those are considered world class rifles. So are the Accuracy International weapons that use thier own style action. But, some of the best rifles in the world, which are made by Tactical Operations, use that same old 700 action. I think this just goes to show that the action is more of personal preference and not an indicator of accuracy.
And yes I do think that custom semi-auto rifles can compete with these aforementioned rifles. For example, the whole Les Baer line is guaranteed to shot a .5 MOA. The PSG-1 has to shoot 50 rounds of match ammo into an 80mm (3.14") circle at 300m before shipping. Other manufacturers that can compete are American Spirit Arms, Blake's Customs, and Springfield Armory's m25 Whitefeather Tactical