I'm just an AR newbie here, but I definitely would not fire it just yet...it will probably short stroke on ya, because chances are that the barrel vent hole is not aligned with the gas block hole, eh. There are supposed to be dimples in the barrel to align the setscrews, so the fix is probably (???) realtively simple. Then again, some of those things were assembled with loctite, taper fit, etc., who knows?
Hey, guys, can ya hook a brother up here?