I have a 6x45 (6mm-223) upper.
It has a DPMS receiver and gas block
Model 1 Rifle Length Forearm
20" AR-Stoner 1-8" Twist SS Barrel
The barrel is threaded, and the whole thing is extremely accurate.
I am getting .5" or less moa from muzzle to 500 yards.
Check out the 3 shot 200 yard .327"...