I have a 16" 1/9 twist, 264 LBC chamber. It was very accurate for me when I first took it out. Sub-MOA at 200 yds. The handguard worked itself loose and the face of the receiver got beat up pretty bad. I had re-tightened it, but I was only able to use a strap wrench, so I wasn't really happy with the torque. I noticed the groups increasing to over 2 MOA at 100 yds the last time I took it out. Based on what I know what the barrel is capable of, I think the receiver was the problem. Loose fit between barrel and receiver, beat up face, and inability to properly torque the barrel nut.
Here's what the receiver looked like (the barrel had close to 1/16" of play at the muzzle with no barrel nut).
I decided to upgrade to a VLTOR MUR-1 and JP VTAC tube. First thing I noticed, wow. The barrel is SNUG into the receiver. No play at all once it was in there. I torqued the barrel nut (with moly grease on the threads) to 30 ft lbs, loosened, torqued to 30, loosened, then set the torque wrench to 50 ft lbs. On the last time, the gas tube nubs lined up perfectly right as the wrench clicked. I'll be taking it out tomorrow to shoot it. I'll let you know how it turns out.