The Essentials of a Precision AR-15

[MistWolf]

As always, great post Molon

Its like not a bolt gun where the bolt face and lugs are part of the entire bolt group. The AR bolt group is basically 2 main pieces where a bolt gun is one main piece. The AR bolt basically floats in the bolt carrier, and when in the locked position can be moved slightly just be finger pressure.

I do not believe you would notice any difference between an in spec and within head space USGI carrier and the fancy BCG's due to the above reasons. With a bolt gun accuracy can be improved by blueprinting/truing the action. Its just not possible in an AR to get the tight fit a quality bolt gun has.

The laws of physics don't change just because we're talking about the AR. The interface between the bolt lugs and the recess is important regardless if it's bolt & carrier design or simply a bolt.

Being a two piece bolt design isn't why headspace is within spec when changing out barrels & bolts. It's because the tolerances are tightly controlled. I believe it's the barrel, barrel extension & barrel nut design that allows the tolerances to be held.

Not all bolt actions have a one piece bolt body. As I understand it, the Savage use a two piece bolt and a barrel nut. Mauser type bolt actions require the barrel to be screwed into place to a certain torque spec. This makes it difficult to match actions, barrels and bolts so that they are interchangeable without it changing the headspace. Further complicating things is the bolt locks into recesses cut in the action.

I don't have an AR with me to check, but I don't think you can move an AR bolt back & forth when it's locked into battery That would allow the headspace to change and could cause dangerous fluctuations in pressure. It would also allow the lugs and recesses to be battered to death with each shot. The bolt carrier, yes. That can be moved slightly without unlocking the bolt.

The only way to determine if a National Match carrier will improve accuracy is to shoot it alongside a normal carrier. The theory is sound as it reduces the axial play of the bolt carrier within the receiver