For the visual learners:
h ttp://www.jesseshunting.com/photopost/data/500/medium/Zerobulletpaths.jpg
50yd zero is blue. 100 yard zero is green. Note which trajectory stays closest to the sight line at ranges out to 300 yards.
Total agree cuz that's what the gong is set-up for223/556 is so flat shooting I would go with 200 meters/yards