Help Identifying This Casing Scratch and Scruff

[Desert Dan]

I'm hoping someone can help identify what is causing the small scratch and scuff that is visible in the attached photo. I recently cleaned out at least most of a carbon ring in my Christensen Arms Ridgeline and suspect it might be leftover from that but if it is something else I want to get it identified and fixed. The pic doesn't do the best job showing it but in person it is obvious once you see it. The case shown is a brand new, unfired piece of ADG 6.5 PRC brass. I had taken the firing pin and ejectors out to measure the distance to the lands when I experienced some resistance and when I chambered a new piece of brass this was what it showed. It also did it with a piece of twice fired, unsized Hornady brass. I should point out that the extractor gives pretty decent resistance when chambering a round that is reduced significantly when I lift the bolt and close it again without ejecting the casing (once the extractor has clipped onto the casing). At this point I don't know if this is somewhat normal or if I need to find the problem. I want to avoid over cleaning with bore paste if it's not still a carbon ring. Thanks in advance.

dan

 

[Don Qui Puncher]

I had a similar thing with my Tikka, I had to bump the shoulder back .003 to eliminate resistance I think it’s a small chamber. New lapua brass has slight resistance, once fired has a lot. I haven’t had any issues since bumping the shoulder back, maybe try bumping back a new case back and see if it goes away

 

[Desert Dan]

Ok I might give that a try. I broke down and ordered a borescope (thanks Amazon next day delivery) so that will helpfully tell me a lot.

 

[Wrench]

Sharpie your barrel right where the action meets it....inside the action. Im betting it has a sharp edge as it goes from ramp to barrel.

 

[Desert Dan]

I had a similar thing with my Tikka, I had to bump the shoulder back .003 to eliminate resistance I think it’s a small chamber. New lapua brass has slight resistance, once fired has a lot. I haven’t had any issues since bumping the shoulder back, maybe try bumping back a new case back and see if it goes away

Sharpie your barrel right where the action meets it....inside the action. Im betting it has a sharp edge as it goes from ramp to barrel.

Did you guys find this was a problem from the beginning? I pulled a pile of once fired brass and none of them had the scratch on it so it developed over the course of the first 350 shots. Frustrated with this.

 

[Sweetyzfd]

You can polish the chamber a bit with some barrel safe polish. Might help a bit