The rubbed spot on the inside of the extractor cut is in an area that is not normally blued on a Krag but because this receiver was mistakenly blued (which was the 3rd miscue with this job and ruined the original finish) it offered a visual contrast not normally seen at that location.

It does appear the extractor cut on this barrel is angled ratherthan being parallel to the barrel that caused it to be off slightly and bind up the extractor. This was obvious enough for BR to pick it up from my picture and suggest the simple  solution. It took longer to go to the garage to get the stone than was spent actually stoning. So little was taken off I doubt anyone could tell eyeballing it.  There was no way I was sending this back under warranty or not for an adjustment of a couple thousands which is all it took.