What in the world is this?

[Gregg C]

Working on a puzzle with 33XC. Try to keep it short.
Ran a pressure ladder awhile back. Picked a load, going to run some thru it, start playing with seating depth. Ladder showed 121 grains LRT under 300gr SMK to be max in my rifle, at 3243fps. Loaded up 40 rds at 118.5, looking for somewhere around 3100ish, and off I went.
First shot, 3208, hard bolt lift, smeared case. 2 more showed similar results. Stopped. Pulled bullets, dumped and weighed charges, no surprises there, 118.5. However, I discovered I hag about .009 of interference fit between case out of neck bushing and loaded neck.
Here is the reason of this post, tho. Went into chamber with bore scope looking for carbon ring. What I found has me puzzled. Any ideas?

 

[Gregg C]

After cleaning

 

[Gregg C]

ok here is cleaned

 

[Gregg C]

With a case inserted

 

[338 dude]

Looks like a small dimple. I don't know how it was created. Definitely looked better the more it was cleaned.

 

[338 dude]

With the early signs of some fire cracking and the dimple, a small setback would clean up everything.

 

[Gregg C]

Pretty ugly with carbon on it, for sure. I think it's positive, as in, sticking up. I actually sort of think it looks like weld splatter. It's really small. Maybe shorten my dress .010 and forget it.

 

[Gregg C]

Brass. Shorten my BRASS(stoopid fone).