I was watching the Magpul Precision Rifle video today, and came across the segment where Todd Hodnett discusses clean bore vs cold bore. He mentioned something I've never heard of before; that he never cleans the copper fouling out of his barrel. The reasoning was (as I understand it), that in the process of zeroing, the barrel begins to strip copper from the rounds. By the time the rifle is dialed in, the optic is set to POA=POI when the barrel has fouling in it. By cleaning out that copper, the gun will shoot off POA until the copper from the fired rounds has once again settled into the rifling and the barrel returns to the condition it was in when it was zeroed. Does the same apply to an AR barrel (I figured this was a specific enough question for the technical forum.)?

