Thanks for the ideas of what to look for.
The mags are in real good shape, no feed lip problems. I initially started recording which mag was being used when the problem happen, but there is no relation ship using either 20 or 30 rd mags, with or without green followers.
The scratches are definitely coming from the barrel extension lugs during loading. The scratches are also showing up on the bullets. I have stopped a couple of times with a round in the chamber and have ejected it very slowly to check for scratches. There is definitely brass on the bottom lug left hand side.
The problem has occurred since the beginning. I attributed the problem in the first 10 rounds to a new bolt and barrel, but even though the problem is becoming less frequent, it is still occurring.
I have cleaned and inspected the chamber before and after range sessions, but it is relatively tight and leaves very little powder residue on the cases after firing. I thought the tight new chamber might be causing the problems. However, I also have a tight Kreiger stainless barrel I shoot NRA High Power matches with and have never had this problem with it. No problems with my 24" Bushmaster barrel either. All of my barrels are on separate rifles, so no parts are shared between them.
Problem has occurred with Federal, S&B, and reloads. I use the same ammo in the other rifles with no problems. Ammo chronos to about 3100 fps.
I lube this rifle the same as the other two. It is not dry, but not dripping wet either.
Is it possible for me to use a Dremel and stone to round/smooth the edges on the barrel extension bottom lug?
Jarrod, any new ideas?