New AR owner with a sighting question

This is a discussion on New AR owner with a sighting question within the Defensive Rifles & Shotgun Discussion forums, part of the Related Topics category; I recently purchased a RRA AR15 and went to the range to sight it in (100 yards). The instructions I've read use the front sight ...

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Thread: New AR owner with a sighting question

  1. #1
    Senior Member Array KoriBustard's Avatar
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    New AR owner with a sighting question

    I recently purchased a RRA AR15 and went to the range to sight it in (100 yards). The instructions I've read use the front sight to adjust for elevation and the rear for windage. However, the rear sight also has an elevation adjustment. So here's my stupid question. Why is their also a rear elevation adjustment when the front sight (with detent) is for elevation adjustments? Thanks!
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    VIP Member Array cmdrdredd's Avatar
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    Everyone has a different sighting method. I usually would put the front sight to center and use the rear for all adjustments if it also has elevation. Many rear sights only have windage adjustments (left and right).
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    Senior Member Array KoriBustard's Avatar
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    Quote Originally Posted by cmdrdredd View Post
    Everyone has a different sighting method. I usually would put the front sight to center and use the rear for all adjustments if it also has elevation. Many rear sights only have windage adjustments (left and right).
    I believe all AR's have both adjustments, so not sure when to use one vs. the other (or if they're the same). Certainly the rear elevation adjustment is easier to make as it requires no tool. So still a bit "confused."
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    Distinguished Member Array Exacto's Avatar
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    Get close using the front sight for elevation, then fine tune with the rear elevation knob.
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    Senior Member Array KoriBustard's Avatar
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    Quote Originally Posted by Exacto View Post
    Get close using the front sight for elevation, then fine tune with the rear elevation knob.
    Okay, thanks. Back on the range Sunday and I'll see how that works.
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    Yup, front range is for major adjustments, and generally, is generally only adjusted once.

    The rear sight adjustments are more for fine adjustments, as well as adjusting elevation based on range.
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    VIP Member Array aus71383's Avatar
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    The rifle is designed to be sighted in at 300 yards. Your rear sight will have elevation setting that is either 8/3 (an on A2 upper receiver) or 6/3 (on a carry handle rear sight or LMT rear sight).

    We don't actually sight our rifles in at 300 yards - too much walking.
    For the bullet to hit the target with the sights aligned at 300 yards, it has to go up first. This means that the sights will be parallel with the ground, and going straight to the target - but the barrel will be tilted upwards. The bullet will be in line with the sights at 300 yards when it hits the target as it falls down. It will also be in line with the target at 36 yards on it's way "up" above the sights. This 36/300 zero pretty common. Another common one is the 25/200 zero. In any case - you won't have pin point accuracy - it will be +/- a couple inches in between "point blank" and your zero, due to the trajectory of the bullet.

    If you want to be able to use your rear sight to make elevation adjustments for distance, you need to sight your rifle in at 8/3 or 6/3 (whichever is the case with your rifle). The "3" means 300 yards. The "6" or 8" means 600 or 800 yards. At 200 yards, usually 8/3-2 is used. When I'm at 500, I set it right on 5 and hit black, or I set it at 5-2 and aim at the top of the target, or 5+2 and aim at the bottom of the target.

    The rear elevation turret makes 1 MOA adjustments per click. The rear windage adjustments are 1/2 MOA. I think the front sight post adjustments are 1.25 MOA per click on the 20" barrel, but I'm not sure about the carbines. It might be 1.5 MOA or something close to that. In any case, if you need to adjust an inch at 25 yards, it will be "several" clicks.

    The front sight should be adjusted while "zeroing" the rifle at either 25 (8/3 or 6/3 minus 2) or 36 (8/3 or 6/3) yards. Be sure the elevation turret is down when you're doing this. If it is on "8" instead of "3" there will be a big gap between the rear sight housing and the turret - about 1/2" or so. It will be obvious. If you crank it all the way down, then go up until it's on 8/3 or 6/3, you have it right.

    A good idea if you plan on making any windage calls is to find the center of your windage adjustment. Usually they have somewhere around 80 clicks of adjustment. Crank the windage all the way to one side, then count the clicks as you move it all the way over to the other side. Divide by 2 and center the windage. Then when you are "zeroing" your sights, you will be able to record your windage adjustment at "zero". Chances are good it won't be centered....usually 10 L or R is expected, something like 20 is worrisome.

    I didn't proof read this.... Hope it helps.

    Austin
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    VIP Member Array Smitty901's Avatar
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    Do the AR by the book. The AR is different because of the round and the site height above barrel
    You may find this interesting and help full.
    Zero Distance for a Home-Defense AR-15 | Shooting Illustrated

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    Start at 25 yards the front site is the bad kid ( it does the opposite of what you tell it ) the rear site is the good kid ( does what you tell it )
    bullet impact is opposite for the front site movement and same for the rear site.

    I remove the bolt carrier and set the upper on a bag on the bench. look thru the barrel and then without moving the complete upper look thru the sites. See if they are close, if so put it together and shoot it. You should be on paper at 25 yards. Measure the target and make your adjustments. At 25 yards your rifle will be zeroed for 250-300 yards ( depending on ammo and barrel length). So if you are going to shoot at 100 you will need to make an adjustment for elevation. I try to set mine up so all of my adjustments can be made on the rear site. Not always possible. Good luck and I am glad you got one!

    Also make sure you can shoot a tight group at 25 yards if you can't practice, practice practice. all of the site adjustments are worthless if you can't shoot a group.

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    VIP Member Array Smitty901's Avatar
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    Save your self a lot of problems and wasted time read study do it works it is correct.
    https://sites.google.com/site/jimmyh...mc25mar-15zero

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