I've only put a couple hundred rounds through my BCM 9" SBR build but I've been happy with it so far.
I was able to put together a couple of 3/4" five shot groups at 50 yards with all rounds touching with Barnes 110 VOR-TX TAC TX rounds when zeroing my 1-6 scope. About the same size groups with Sig Sauer Elite 220gr Subsonics as well.
Just for reference, I am normally only about a 1-2 MOA shooter at 100 yards anyways. So I'm sure this barrel would perform better with a better shooter.
It handles well even with a Saker 7.62 hanging off of the end of it. And it's eaten all the factory ammo I've fed through it so far (Barnes, Hornady 125 gr American Gunner, Sig Elite 125gr and 220gr, PNW Arms 125gr Match and 220gr Match).
Also, my ammo cycles and locks back on the last round with a Spikes T3 buffer, Sprinco white spring and the Saker. Supersonic cycles well without the Saker. I haven't tried subsonic without the Saker on though.