Think "gas". If not properly gassed you will have both FTF and FTE problems.
Think "bolt speed". This,due to properly gassed,and another several major and a ton of minor things.
Would suggest that you use the MagPul brand of mags with this gun.
Please don't take this wrong. If you understand the mechanics of an AR,you can easily build a pistol. However I would highly reccomend a bbl of between 10.5 and 12.5 inches.This,for velocity reasons and muzzle blast . . ESPECIALLY if using a brake. The vels of a super 300BLK drops off pretty fast in the super short bbls. The muzzle blast is pretty much unbearable unless you are using a can with subs. Even using a linear comp.
Gettin' the gas right is much easier in the longer bbl'ed pistols also. Has seemed to me that the diff between 16" and 10.5 and especially 12.5 inches of bbl is not that great in getting the gun to run properly. 8.5 inches is a different story. But again,it can be done. ---- SAWMAN