I have a loose spot in a # 1  Rolling Block barrel  just before the octagon goes to round. I bought a cheap  bore scope to see what was going on.  Here's what i found.  The first photo is a straight on view and I can see 2 sets of lines in the grooves.  The second is  a side view close up one if the grooves.  There is nothing noticeable on the exterior of the barrel  and the lines/scratches/marks don't scribe the lands , so I don't thing it's a "crack" in the barrel.  I'm guessing it is a relic left over from rifling the barrel.  I can't see any change in width, but can feel it with a cleaning patch. All of my shooting so far has been brass forming and velocity testing , not with accuracy, but it's seems to be fairly accurate.   Has any one else seen this? and what do you think was the cause? 

Someone stuck a bullet at some point and had trouble pounding it out?
Todd