Quote:
Originally Posted by ohnomrbillk
In a study done which you can find here: www.riflebarrels.com/articles/barrel_life1.pdf , the conclusions note that, "there is peeling of the oxide layer by tangential cracks under the surface resulting from shear stress." They note that chrome lined bores do the same thing, but in less time. That does not sound like accuracy to me.
If it made for the most accurate barrel, benchrest shooters would be all over it. For a battle rifle like an AR, it may be ideal.
George at GA Precision has told me most US sniper rifles pass accuracy as long as they can hold MOA accuracy. No doubt many shoot better than that, but they are not required to.
I guess answering the "are they accurate?" question is subjective to what the buyer defines as being accurate. By looking at the suggested premium barrel manufacturers, I'm guessing the expectations are high. |
We don't use plasma nitriding so this paper does not apply to AAC barrels. Remington tested their nitriding process and found that it lasted 60% longer than hard-chrome. As for accuracy, it has no more accuracy potential than a stainless barrel. What I claim for AAC barrels is - the accuracy potential of a stainless barrel, but lifespan potential greater than hard-chrome.
I don't disagree with you that benchrest shooters have a different standard of what is good from other people, and in being clear, the AAC barrels have more of the design philosophy of an AI rifle or sniper rifle than a benchrest rifle. For example, a benchrest rifle will have freebore probably below the legal minimum - perhaps 0.3085 or so. The AAC barrel is going to have freebore around 0.3095. This is done for a few reasons...
1. To keep pressure down.
2. To reduce the chance of a stuck bullet if you extract before firing.
3. To allow for a cartridge to chamber more easily, even if there is bullet runout.
The AAC barrels are made very carefully to the drawing and the chambers are verified with ball gauges and depth micrometers, but the drawing does not go below SAAMI min as many custom guns would do. If you want to win an accuracy contest above all other considerations, you probably do want to violate minimum dimensions.
For example,
SAAMI 0.308 Win freebore is 0.310 minimum.
SAAMI 0.308 bullets are 0.309 maximum.
Custom gunsmiths 0.308 chamber reamers often have 0.3085 freebore.
This is not something an engineer who understands geometric dimensioning and tolerancing would allow. Perhaps every bullet a custom gunsmith saw so far was 0.3083 or smaller and they "never had a problem" with a 0.3085 freebore. Their guns shoot better during a magazine test and the gunwriter also had no problems. This causes the custom gun maker to claim they are better than a $6,000 AI or Remington XM-2010. Fine, until the user in the field extracts an unfired shot and the bullet stays stuck in the chamber, and powder is everywhere - and then the hostage-takers kill the hostage.
That is what I try to do for the barrel - well made and accurate but not at the expense of reliability under extreme conditions.
Also, pressure goes up about 3,000 PSI with small changes:
http://www.border-barrels.com/articl...Consortium.htm
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