11-25-2013, 05:08 AM
Most production rifles don't have evenly bearing bolt lugs. This is true of hunting rifles, as well as AR15's. You can check any of your rifles with Dykem and confirm this for yourself. It's simply a product of slapping production guns together on an assembly line where cost benefit analysis doesn't warrant ensuring 100% contact between the bolt lugs and their recesses or barrel extension.
My leaning is towards the durability of the system, then accuracy. Since we're dealing with a bolt geometry in the AR15 that was designed around the .222 Remington in as light of a gun as possible, there isn't a lot of bolt lug mass to begin with.
Yes, the barrel manufacturers "should" ensure that the barrel extensions are true to the barrel, and they "should" ensure that the bore is concentric to the OD, and they "should" ensure that the barrel breech end threads are true and concentric to the bore. Unfortunately, these are all very rare to find on a production rifle.
Same with receivers. Notice that NugginFutz stated that half of his AR15 receivers were not true on the face? Everything should be true off of the center of the bore. The more parts that are true and concentric to the bore's center, the more balanced and accurate the system will be from both a longevity and accuracy standpoint.
If the receiver face is not true, it will cant the barrel off to one direction, so that the bolt lugs only engage on one side. This configuration will in fact break bolts, shearing lugs off in very few rounds. On the billet receivers made by well-renowned companies like LAR, Seekins, and Mega Machine, you have a much higher standard of QC when it comes to the receiver face being trued to the bolt carrier raceway.
In the bolt gun world, this is why precision billet actions are so popular with accuracy nazi's. Why spend all the time trying to un-suck a Remington 700 action, when you can just get a top-end CNC billet receiver from GAP, Surgeon, Templar, etc.
My leaning is towards the durability of the system, then accuracy. Since we're dealing with a bolt geometry in the AR15 that was designed around the .222 Remington in as light of a gun as possible, there isn't a lot of bolt lug mass to begin with.
Yes, the barrel manufacturers "should" ensure that the barrel extensions are true to the barrel, and they "should" ensure that the bore is concentric to the OD, and they "should" ensure that the barrel breech end threads are true and concentric to the bore. Unfortunately, these are all very rare to find on a production rifle.
Same with receivers. Notice that NugginFutz stated that half of his AR15 receivers were not true on the face? Everything should be true off of the center of the bore. The more parts that are true and concentric to the bore's center, the more balanced and accurate the system will be from both a longevity and accuracy standpoint.
If the receiver face is not true, it will cant the barrel off to one direction, so that the bolt lugs only engage on one side. This configuration will in fact break bolts, shearing lugs off in very few rounds. On the billet receivers made by well-renowned companies like LAR, Seekins, and Mega Machine, you have a much higher standard of QC when it comes to the receiver face being trued to the bolt carrier raceway.
In the bolt gun world, this is why precision billet actions are so popular with accuracy nazi's. Why spend all the time trying to un-suck a Remington 700 action, when you can just get a top-end CNC billet receiver from GAP, Surgeon, Templar, etc.