Quote Originally Posted by earl39 View Post
As you said the pictures are a little out of focus but the middle one shows a slight ridge right at the rifling. That is in the freebore area and will not have effect on the brass. The other two i can't determine exactly where the burr is in relation to the chamber. That said it is your barrel if you want to try to polish it out go for it.
Back to had to hit the bolt carrier to get it to unlock, did you pull the charging handle and slam the butt of the rifle on the ground to try to get it to unlock? That is the common and accepted way to clear the weapon when it won't unlock before going to more extreme measures. The scratches on the brass really look like they are made by the locking lugs in the barrel extension BUT with the two photos not being clear in relation to position you can't rule anything out yet.
Just wondering what your experience level with the AR platform and trouble shooting is?
I tried the usual technique. Pull charging handle? A gorilla couldn't budge it. Slam stock down? No effect. It took about 3 raps with a hammer and brass punch on the back of the bolt carrier to dislodge it.

The ridge you see with the bur in it runs all the way from the beginning of the rifling to the start of the shoulder. I assume it is where they stopped the reamer during chambering. that worst area with the bur in it is just about the middle of the neck. You can see it in all three pics from rifling to shoulder.

Can't hurt to smooth out the reamer marks. If that doesn't fix it I will move on to the next thing.

I have built a few.

I don't understand how the locking lugs could have marked the neck of the brass. The round was single loaded into the chamber not the magazine and was most definitely not ejected from the chamber but slowly pulled out by hand.