superdown,
I have a right hand 5.56 M4 variant built by Stag. I bought it about two months ago and have 200-300 rounds through it. It has very close tolerances as evidenced by its tight upper to lower receiver fit and the inability of some surplus magazines to be inserted into the mag well. It works fine with the new 30 round magazines but balks at accepting some of the older 20 round surplus magazines I have, which may have many of the attending problems inherent in the AR magazine due to being rejects offered on the civilian market or an extended service life. Reminds me of the M1 Carbine magazine crap shoot of the old days; some surplus mags worked flawlessly, others did not. The finish on the rifle was surprisingly good for this type of firearm, and the receiver's hues matched perfectly. The sights are properly installed and registered; this allowing easy sighting in and the ability of having the sights perform as per their markings. The rifle is also fairly accurate, not a tack driver, but capable of 2 MOA at 100 yards with the aperture sights off a sandbag. I have had no failures to feed and no jams. There was no "break-in period" as required by some rifles to obtain proper functioning. The accuracy deteriorated after about 50 rounds and then returned and stabilized after about 50 more rounds. This is something I have seen in many chrome lined military barrels, once termed "shooting in". The trigger was a little stiff, but it has smoothed out and actually presents a decent pull cycle for this type of weapon. The rifle is accurate enough that I may use it meaningfully at 300 meters for offhand shooting. Connecticut Machine and Tool (CMT) is the parent company and the source of parts for Stag. CMT is a military contractor.
I purchased the upper receiver form one distributor and the upper assembly from another. This allowed me to save about $125 over purchasing the complete rifle from one distributor. AR15.com has a forum termed "Equipment Exchange" where this strategy becomes apparent.
I will be purchasing Magpul Industries magazines (PMag) in the future. These are a polymer construction and have several features that make them remarkably serviceable. I do not know if they manufacture 6.8 magazines, but the companies offering the rifles catalogue such; and since they are new they should work properly.
