I just bought a new Armalite N.M AR15.  My first attempt to zero it in wasn't the greatest experience.  I was shooting very high out of the box at 100 yards (not even on the paper.)  So  I moved in to 25 yards and made my sight adjustments.  I didn't realize that the Armalite front N.M sight is tapered and that the wide part of the sight needs to face the shooter.  So basically it needs to me moved up or down in complete revolutions.   Well I didn't do that and I think it resulted in making the front sight post canted to one side.  As a result to get a 100 yard zero my rear sight had to be cranked WAY over to the right.  I called the shop that sold me the rifle and they said to readjust the front sight so the wide part faced me, and to re center the rear sight.  My range only has a berm out to 200 yards, so I think I want to try the 50/200 yard zero.   My question is, where should I set my rear sight elevation to get started at 50 yards.  Out of the box I think it was around 5.  When I was shooting at 100 yards I think I had it cranked down to 1.  Sorry for the long post, but I want my second attempt to zero in this great rifle to be better than my first.

Does it have a set-screw or clamp-on style front sight? If so, set the rear sight to mechanical zero. Separate the upper and lower, remove the BCG, rest the upper on bags or in a vice, and boresight and adjust the front sight's windage to match, then lock it down.





My original front sight post's base (the part with detents) was about flush or just below flush with the deck. Perhaps start around there with the proper orientation and move up or down in whole revolutions until it boresights close, then fine tune with the rear sight. I like my 100 yard zero about 3 MOA above bottom.



ETA: even with a pinned front sight, starting with mechanical zero is a good idea.

competitors have different eyes, and as the national matches seem to be mostly under 18 or over 60 yrs old, there is a big selection in front sight posts that are CMP/HP legal that help people of different ages focus on the thing.  size seems to make a big difference.

one of many examples of quality retailers:
http://www.whiteoakarmament.com/xcart/home.php?cat=287&sort=orderby&sort_direction=0&page=2

you can get a front sight post here that is .040 .045 .052 .062 .072 or standard width.     they are $10.   for that price, you might want to try a different one.


your choice of zero will depend entirely on what type of target you shoot.    if you are shooting the standard national match bulls eyes, then you can do a center hold, 6 oclock hold, line of white, flat tire, reverse flat tire, etc.   as far as distance, just about everyone uses a 100 yard zero.

if you're shooting some other type of target or a wide range of targets, e.g. plinking, then it gets a little more complicated.  6 oclock gives you the best view of the target, but isn't very precise since you have no idea how big your target will be.     as far as distance, it is also more complicated, and you need to think about your offsets.  i.e. if you're trying to hit the A zone on an IPSC head at 10 yards, you would normally hold the top of the head with a 50/200 yard zero, but how do you hold the top of the head with a 6 oclock sight picture?  hmm.....

If you're zeroing it for xtc matches, the 50/200 will not work. You'll need to establish a true "zero" at all distances, i.e. 2,3, and 600 yards. Zero it at 100, and then add the "come ups" to get on target at 2,3, and 6. Make sure to count the "clicks" up from bottomed-out and record them for future use. Also, use nail polish or a paint pen and mark the elevation index as well. The 3/8 or 3/6 will be basically useless in xtc.
Also, zero using your chosen match load(s).

As mentioned you need to know of you have a windage adjustable front sight. You also need to know if there is a set screw below the front sight post. If so it needs to be backed off to adjust the front sight height.

I usually bottom the rear sight and lower the front post (1 complete revolution each time due to blade taper) until it shoots low then set it one revolution higher so it barely shoots high. That is done at 100 yards. Then I adjust the front sight windage, if adjustable. After that I thread lock the front sight screws. From there all adjustments are made with the rear sight to center on a 100 yard target. Once zeroed, I mark the sight knobs.

You need to raise the front
sight post to make the rifle shoot lower.