Gunsmithing Question about marks on shoulder/neck and bore shoulder

I don’t see how the mark in your chamber is related. Did this brass hit the ground?

Looks like normal AR10 activities of ejecting brass. The scar is even worse.

1) The dents on the shoulder appear to be from the brass hitting the brass deflector while being ejected. This is pretty common on AR rifles. Depending on the exact rifle and it's specific timing, those dents won't always be in the same place but they are typically in that area. I suspect the scratches on the neck are similarly ejection related.

2) It appears to me that the area you have photographed with the bore scope images shows part of the leade and the start of the lands and grooves of barrel. On a 6.5CM, this area is well in front of where the brass reaches as the 6.5CM has a pretty long leade. The streaks I see in the leade area look like maybe a little bit of carbon build up that escaped your cleaning. They look very thin and not significant.

I don't think you have any problems. Looks like pretty normal ejection marks and a slight amount of fouling in the leade area. A little uneven carbon on the outside of the neck is normal as well. There is always a little bit of filth that slips out before the pressure in the case builds to the point that it is effectively adhered to the chamber walls.