I am not going to get either the Sig 556 or the FN FS2000. I was planning on getting the FS2000 until I read this month's American Rifleman--some idiot at FN forgot to put a last-round hold-open device on the damn thing. No thanks as over $2K. As for the 556, look closely at it...it is essentially a piston upper on an AR lower but without the myriad of spare/custom parts available for the AR platform. Better to stick your money into ammo and training than the next new toy. I predict that the Colt LE1020 and HK416 piston uppers will soon be available to the public (one way or another), and I'll just wait.