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Using a ballistics program input with the AR sight height and M80 ball ammo I get -1.49” low at 25 yards with a 100 yard zero.”
Not all AR’s have the same sight height. I use taller scope mount, 3 inch sight height, I get 1.91 inches for 100 yd zero.
Also I recommend using a 200 yd zero for .223 or any high velocity round. This will give you a greater point blank range than a 100 yd zero. In other words you don’t have to worry about hold over until 250 yds or so.
Zero range is a personal preference thing. I use a 300m zero ofr iron sights. Many scopes have ballistic reticles as I am sure you know that are intended to be zeroes at 100 and the markings used for holdover beyond that.
The OP would have to fill in more info to be picky about things.