I was interested to Nightforce ( shv and nx8) and Vortex (viper pst gen 1&2) several years ago. I became a fan of both when I had both fall off a shooting bench onto concrete. That was a stressful moment. I picked both rifles up and both held zero and no issues with tracking. I also have 2 sig optics(tango 4 and whiskey 4). i am impressed with sig as an optic manufacture so far. all optics are FFP and MOA. Both sig optics are mounted on 223 rifles.