Just received and unboxed my new 20" A4 melonite upper (SKU 7781740) this afternoon. Very excitedly disassembled it and started inspecting all of the parts. It wasn't long after I looked down the muzzle that I noticed something odd. The barrel appears to be ringed just before the muzzle threads begin. I have not shot the upper, I've only run a couple of boresnakes through it (one tighter than the other). Ring will not go away.
I cannot tell if this is an actual depression in the lands/grooves, or if this is a discoloration effect of the nitride process. I suspect shooting it would give a quick indication, but if this upper needs to be RMA'd, I do not want to shoot it and ruin any chances of that happening.
In addition, the included BCG has primer residue on the bolt head. Are these uppers test fired? Could there have been a squib during testing?
I was really looking forward to shooting this upper soon, but as it stands, I suspect it will be going back into the box.
Will post a photo shortly once my camera has charged up.
This is order #2102030660
eta: the more I look at it, it looks to be more discoloration than depression. I've had ringed .22 barrels before where you could see the depression in the bore. But I would hate to start shooting this upper and find out that it truly was defective. It also doesn't make sense that a discoloration in the metal treatment would appear as a complete concentric ring
Here's are a couple pictures about as good as i can do. may try again later