Re: sig 556 question
Short answer...No. I've had my 556 for about 6 months now and put nearly 2000 rounds through the gun. Overall, i couldn't be more happy. I know no one will believe me, but i haven't had a single malfunction or jam in my gun. Not one. I didn't think that was possible, but the piston system is just that reliable.
Now, as far as range shooting, I've shot mine out to around 600 yards(plinking rocks). I've got a Vortex 4x12x40 on the weapon. As much as i've wanted it to be, this gun simply isn't a long range gun. With XM193, i can punch 3-3.5 inch groups at 100 yards. That's no tack driver, but it's accurate enough to have fun with. I wasn't happy with that though, so i started reloading for it. The aggressive barrel twist definitely favors a heavy bullet. I also wanted to shoot a whitetail with gun, so i wanted a heavy/accurate load. I don't want to get into the ethics of hunting with a 22 caliber bullet, but i will say that my 70 gr TSX dropped a decent little 4x4.
I reloaded 70 gr Barnes TSX bullets and 60 gr V-Max bullets. With the reloads, i can consistently shoot 1 inch groups at 100 yards, but not any better(also 1" groups with 70 gr Hornady TAP). The farthest i've shot on paper is 300, which it did hold 3" groups. If you are looking for a tack driver, you'll need something with a longer, heavier barrel. If 1 MOA is good enough for you, you can expect amazing reliability with this weapon. It's really just personal preference.