The ARMY regs and tecniques are to zero at 25 meters this gives the rifle MOC (minuet of chest) out 300 meters. The goal is to get a center mass hit, and save ammo buy not zeroing at a farther distance.
I have a RRA entry tac I used it for deer, prarie dogs, and 'yotes while I lived in SD.
to zero:
1. sight in at 25 yards iron sights BUIS.
2. I then co witness red dot optics
3. I then zero the red dot optics at 100 yards
4. Then re cowitness the BUIS at 100 yards
I find this gives several advatages to me.....
1. My groups are only 2 inches high at 200 yards
2. I can remove my EO tech and put it back on then confirm zero using the co-witness
3. My groups are 4 inches low at 50 yards
4, groups are 6 inches low at 25 yards.
5. It was also very easy to zero my laser at 100 yards using this technique
If you don't like this idea or do not have access to a 100 yard range try using the 50 yard zero which gives a flatter path of travel (cant' spell tarjectory right now)