well,, i did shine a light down it and it looked good, peeking in from the upper, using good flashlight. I actually reloaded for years, and chased the mythical carbon ring a few times, but being wiser now, ( i think), so i took a step back and said hmmmm. i can't believe a carbon ring would appear after 40 rds. (fully admit i could totally be wrong) so i cleaned it and tried this new ammo and am pretty happy now.
sometimes i think the carbon ring is the "Bigfoot" of the reloading world. kinda mysterious, no real consensus on it, blurry pics (if any), "this guy i know had a carbon ring" etc. would love to see some definitive pics of a carbon ring vs just dirty.
although it is a mystery i would like to solve more, the fed ammo worked fine in my bolt gun (as far as pressure, not impressed by it's overall ES and SD at the time but i figure it would work fine in this AR)
also, i seem to have misplaced my lyman borescope, my garage is,,,a bit unorganized. i retired 12 years ago and my first goal was to organize my garage, 12 years later,,,,,it is still my goal.
but in the meantime, it's shooting acceptable! going to go look for my borescope!
also, big shout out to frank at bartlein barrels a couple years ago. went above and beyond on my 6.5saum barrel issue. excellent customer service, amazing really.