I'll admit it - I don't shoot my SIG 556 much, but I put a Nightforce 3.5-15x50 in a LaRue LT-104 mount on it (it has a Magpul PRS stock on it, so I can adjust the comb to work with the LT-104). It certainly is a big scope for the rifle, but I've heard conflicting reports about the accuracy this rifle is capable of. Should I be able to get the same accuracy from it as I would from a 16-18" AR15?
Well the only way to find out is shoot the darn thing. But yeah too much scope I believe.
I suspect that it would depend on the type of accuracy you are looking for.
The accuracy of my 556 Patrols is very similar to a rack grade AR carbine-like a Colt 6920 or 6721. From a bench, hitting clays at 200 yards is realistic if I do my part. A more accomplished shooter may do better, but I'm just a weekend duffer-not a squad designated marksman Posted Via AR15.Com Mobile
First of all Sick Scope bro. Pics Please
The most important question to ask yourself is what am I using it for. If you're looking for a tack driver 300 meters and beyond then the Sig platform is not the best choice. If the scope is for small game out to 300 yards then maybe, but if you're looking for quick target acquisition during CQB then probably not. I have found that experience is the best teacher. I have had an Aimpoint red dot and a 4-12x on mine and ended up with a Trijicon Accupoint 1x-4x that acts like a reflex site at 1x but gives some magnification for small game at 4x. You will figure it out on your own. Everyone's opinion is different. Figure out what works for you.