Ok, quick range report
I took it to the range this evening.
Function
I put 210 rounds through it on gas setting 4, as recommended in the manual to break it in. I had one malfunction, which was magazine-related: one of the mags, though it looks identical to the others, only seems to want to hold 9 rounds, and didn't seem to want to seat properly at first. After a few times in the gun, it functioned like the others.
I then put another 70 rounds through it on gas setting 3, with no malfunctions.
I then put another 140 rounds through it on gas setting 2, with no malfunctions.
Accuracy
With my Mepro optic, I had a nice cowitness with the supplied MI flip-up iron sights. I set the optic to match the iron sights. I didn't shoot it from the bench - all shots were standing unsupported. Still, at 50 yards I was consistently hitting chunks of wood and clay pigeons on the berm, and putting most of my rounds into life-sized bunny silhouette targets. So, it appears to be at least a 'minute of bunny' gun at 50.
Overall impressions
At this barrel length, the gun seems to be very well balanced. It was noticeably heavier than my 10.5" CSA, but the weight was still reasonable.
The brake was awesome: the concussion, noise, and fireballs were almost as good as my 7.5" CSA. Felt recoil was minimal, as was barrel movement. The brake appeared at first to be mounted improperly, but I then noticed that it appears to be asymmetrical, with the ports looking different. I assume this is to counter the spin of the round?
The safety wasn't as nice as those on the ARs I've owned - it was stiffer than I'm used to.
I really liked the non-reciprocating charging handle, and the location of the bolt catch/bolt release.
The FAST stock was nice, but the cheek piece has only two positions - a third, higher, position would be useful with the optic I'm running.
I put 420 rounds through it relatively quickly, and noticed the railed forend became quite hot. I'll be mounting a VFG to it before I take it out again!
Overall, in my opinion it is a very well-designed rifle. I'm very pleased with this gun, so far - it appears to be a keeper
Edited to add: I just noticed this morning that the stock has come a bit loose from the receiver. Time to break out the Loctite!! lol