I have a pile of AR parts and decided to buy a 6mm ARC barrel (16” Proof, 1/7 twist, rifle gas system) and cobbled together an upper. Took my 3-gun lower and a Leupold 1-6 and got some Hornady Black 105 gr BTHP. I had a couple of ASC 6.5 Grendel mags which worked well. Zeroed at 50, a tiny cluster, and shot a bunch of steel at 100, much of it with a TBAC Ultra 7 6.5 can. 60 rounds, lots of fun, no malfunctions, noticeably quieter than 5.56. Chrono’d 5 rounds at 2580 fps.