As has been said, the short answer is that yes, bolt action, all things equal, will be more accurate. When the bolt slams forward on a gasser, it has the potential to set the bullet back a bit AND set the shoulder back a bit. With long range loads IBR shooters, and to a lesser extent me who shoots 1k F-CLASS, take great pains to ensure a consistent case dimension and cartridge base to bullet ogive. At 1k yards a 0.002 bullet setback in my comp gun could change POI by 1/2" or more. Couple that with a smaller case volume due to shoulder setback and it compounds.
Then, if the bullets are deformed in anyway when being violently stripped off the mag, that would make matters worse. IBR and a couple guys I have been shooting with will uniform the bullet tips which would be undone by such violence when chambering.
Finally, there is the trigger....I don't know about you, but I wouldn't put a 4oz trigger on a semi-auto.
Don't get me wrong, AR's can be very accurate. I have a 1/2" moa load in my Gas piston 20" Varmint barrel AR that I shot an F-TR match with, 562-18x. And my AR 10 Ruger SR 762 is 1/2-3/4 moa with my Federal GMM cloan hand load.
But my F-CLASS rifle shoots 3/4-1" groups at 300 yards, all day, every day, no fliers..and I don't mean that is the best it will do, I mean that is what it does at worst on a calm day. Not gonna happen in either of my high dollar AR's.