Some people spend too much time and effort worrying about "zero" ....
and I admit to being one of them.
With my personal AR 15, I've tested accuracy and zero with about a dozen different types of ammunition. Given that my AR 15 is a shorty 10.5" LMT, wearing a 1.75 - 5 X variable scope, and the range closest to me, where I shoot the most only goes out to 100 yds., and given that I've chosen to optimise my AR for fast close CQB shooting rather than accuracy at distance,
my effort here is probably overkill.
I chose to zero for 100 yds., with the ammunition I have the most of,
62 Gr Win white box .223 Ball ammo. I have also tested my zero @ 100 yds with several different loads, and discovered that with different ammo,
zero can vary up to 3" at 100 yds, and this variation in zero may be horizontal as well as vertical.
However,
no matter what ammo I use, if I do my part, I am pretty confident of a hit on a clay pigeon @ 100 yds.
Good enough for what I want my AR to do for me.
AND,
since I am shooting both .223 AND .22 LR,,
and do most of my practicing with my CMMG .22 LR conversion @ 25 yds.
I also have to consider ZERO @ 25 yds with .22 LR ammo.
With the several different brands of .22 LR ammo I've tested, the zero varies up to 3" @ 25 yds . Again, this variation can be displaced horizontally as well as vertically.
"Zero" is a relative term ....
what works for one brand of ammo, and one rifle, and one shooter, on one range, may not work for any other combination,
but for me,
for quick and dirty practice at the ranges I am shooting, where I know any miss will be my fault, not the zero or the ammo variation,
ZERO IS REALLY NO BIG DEAL. ...
even though,
it seems,
I've made it into one.
YPMMV
LAZ 1
[;{)