Well I shot a few rounds through it yesterday. I had some old ammo left from the dead 260AI barrel. I chambered just a little snug...first shot bolt lifted fine but didn't want to extract.
...I had this happen before and my first thought was unfortunately what it was...a small groove in the chamber about .250" from the neck.
I couldn't see it with the naked eye but the brass sure let me know.
Took barrel off and finally after two attempts I got it set back grooveless this time as far as I can tell.
I never had that kind of trouble with any of the others I chambered...after getting a magnifying glass I think it had a speck of a chip stuck to it is all I could think but it was on the shoulder area.
Anyway hope to load a few new rounds and try again.....this time with only a 26.5" barrel.