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What do the increments mean on the elevation dial of an AR-15 rear sight?

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This is something I learned in the GAPP NRA First Steps AR15 class.

 

However - it's late and my memory's a little fuzzy but here's how I remember it:

 

It's how the rifles are sighted in. If you follow regular US military improved battlesight zero, you sight your rifle in at 50 meters and 200 meters (due to the ballistics of the .223/5.56 round). You can crank the 6/3 rear sight up to adjust your zero for longer distances. I can't remember the exact number but IIRC it's moving it to 600 meters.

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They are the yardage for the range that you are shooting. Cranked all the way down, the 6/3 marking is for the 300 yard line. Cranked all the way up, it's the 600 yard line. 6/3 - 2 (two clicks below or down from that marking) is where you start when zeroing at the 200 yard line. Use the same if zeroing at 25 yards. When the windage marking is at dead center, this is your mechanical zero. Start from here and make a note of your clicks to get your groups to point of aim. This is your own personal zero. My zero was always 8 up and 14 right at 200 yards.

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Yep - Because of the ballistics of the .223/5.56 round, if you sight your iron sights in point of aim/point of impact at 25 yards (meters really), you will be hitting Point of aim/point of impact at 300 yards (meters).

 

My AR15 is sighted about an inch low at 25 yards, so that i'm POA/POI at 50 and 200.

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Yep - Because of the ballistics of the .223/5.56 round, if you sight your iron sights in point of aim/point of impact at 25 yards (meters really), you will be hitting Point of aim/point of impact at 300 yards (meters).

 

My AR15 is sighted about an inch low at 25 yards, so that i'm POA/POI at 50 and 200.

 

Interesting. My other question is regarding the sight picture... Is your POI/POA set so that @ 50m, if you keep the top of the post in the center of the circle, thats where it hits?

 

Also, how often are windage adjustments made? I figure it's a one and done kind of thing, right?

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Sight picture depends on the person. Some people like to keep the point of aim at the top of the post. Some people like to cover the target with the top of the post. Personally I like to cover the target with the top of the post.

 

Adjustments are another thing - front sight is for elevation, rear sight is for left/right. Once you have those set, you don't wanna touch 'em.

 

If you've got the time, I'd recommend going to the GAPP (or another) AR15 first steps course. I learned a lot from it.

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Also, how often are windage adjustments made? I figure it's a one and done kind of thing, right?

 

Yes...and no. If the sights are mil-spec each windage click should correspond to 1/4 minute of angle. If you don't care to get into figuring out how to set dope on your rifle (adjusting sights for conditions/range) then yes, set it so that it hits at the range you are shooting, then compensate with kentucky windage (shift your point of aim) to account for wind (or even distance) from that point on.

 

In all honesty, unless you are doing match type shooting, the 5.56 round is a pretty fast mover and you'll be able to hit within 4-6 inches unless the wind is really gusty. My advice is to wait for a calm day to zero your rifle if you don't want to mess around with windage adjustments much.

 

There are a lot of shooters that will move their windage left or right based on the shooting conditions that they are dealing with at that moment. Personally, I would only change it if I was at the 300 yard line or at the 500 and even then it was based on how strong the wind was blowing. Once I get into a sight picture I don't like to come out of it to make changes on the knob.

 

It really boils down to how you prefer to aim and shoot.

 

Edited to add: When looking at the front sight post, you want it centered inside the ring. On reading the first part of your question it sounded like you may have been moving it inside there. I just wanted to make it clear that the front sight post is always centered.

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Adam- Print this out and put it in your gun case, It's everything you need to know.




AR15 Sight Adjustments at 25 Meters
Windage/Elevation Sight Type Barrel Length
(NOTE): for
Dissipator-style
barrels, use 20”
One Click of Adjustment
@ 25M moves point of
impact by:
ELEVATION: FRONT POST
Elevation A1 Front Post (round) 20 " 1/4" (1 MOA)
Elevation A1 Front Post (round) 14.5" or 16" 3/8" (1.5 MOA)
Elevation A2/A3 Front Post (square) 20 " 3/8" (1.5 MOA)
Elevation A2/A3 Front Post (square) 14.5" or 16" 1/2" (2 MOA)
WINDAGE
Windage A1 Rear Knob 20 " 1/4" (1 MOA)
Windage A1 Rear Knob 14.5" or 16" 3/8" (1.5 MOA)
Windage A2/A3 Rear Knob 20 " 1/8" (0.5 MOA)
Windage A2/A3 Rear Knob 14.5" or 16" 3/16" (0.75 MOA)
ELEVATION: REAR DRUM (NON-Match sights)
Elevation A2 Rear Drum 20” 1/4" (1 MOA)
Elevation A3 Rear Drum 20” 1/8” (0.5 MOA)
Elevation A2 Rear Drum 16” 3/8” (1.5 MOA)
(estimated)
Elevation A3 Rear Drum 16” 3/16” (0.75 MOA)
(estimated)
1. Adjust the sights to the windage mechanical zeroing position by one of the following
methods depending on your rifle:
a. (For A1 sights) Flip the rear sight aperture so that you can see the (L). Next, turn
the rear sight windage drum until it moves all the way to the left side and locks. Then,
turn the windage drum back, moving the rear sight to the right 17 clicks so that the rear
sight is approximately centered.
b. (For A2 “8/3” sights and A3 “6/3” sights) Flip the rear sight aperture so the small
unmarked aperture is up. Center the rear sight by turning the rear windage knob until
you align the windage notch on the down aperture with the center notch on the rear
sight base.
2. Adjust the sights to the elevation mechanical zeroing position by one of the following
methods depending on your rifle:
a. (For A1 sights) Adjust the front sight post up or down until the base of the front
sight is flush with the front sight post well. Then, adjust the front sight post 11 clicks
clockwise in the direction of UP.
b. (For A2 “8/3” sights) Lower the rear sight all the way down by rotating the rear
elevation drum counterclockwise. THEN, rotate the rear elevation drum clockwise UP
one click past the 300m mark (the 8/3 mark on the drum).
c. (For A3 “6/3” sights on a 20” barrel) The A3 rear sight differs from the A2 in that
its elevation index is marked 6/3 instead of 8/3. NOTE: the A3 sight has 1/2 Minute of
Adjustment clicks instead of the 1 Minute of Adjustments of the A2 Sight. Thus, the A3
elevation dial must be moved TWO clicks clockwise UP past the 6/3 mark on the drum
to the Z mark. Otherwise, the windage drum and flip-up aperture - and their operation -
are the same as on the A2 rear sight
(For A3 “6/3” sights on a 14.5 or 16” barrel) Same procedure as for A3 6/3
sights, except set the elevation drum on the 6/3 setting, not the Z setting.
3. Once the rear sight is properly set, fire your 5-round shot group.
4. ELEVATION ADJUSTMENT
a. To raise your next shot group, rotate the front sight post clockwise.
b. To lower your next shot group, rotate the front sight post counterclockwise.
5. WINDAGE ADJUSTMENT
a. To move your next shot group to the left, turn the windage knob
counterclockwise.
b. To move your next shot group to the right, turn the windage knob clockwise.
6. Once your point of impact meets your point of aim, your rifle is zeroed. Do not adjust
the front sight for distance; for the A2 and A3 sights, once you are zeroed at 25 meters
by this method, your rear sight drum is calibrated as a bullet drop compensator for 300
meters and beyond using the small aperture. For distances from 0 to 200 meters, use
the large aperture and put the elevation drum on the 3 setting.
SOURCES:
--Operator’s Manual, Bushmaster XM15 and C15, Revision of 2005.
--Field Manual 3-22.9, Rifle Marksmanship, M16A1, M16A2/3, M16A4, and M4 Carbine,
April 2003 with Change 3 of 28 April 2005 (and Changes 1 and 2).
--http://groups.msn.com/TheMarylandAR15ShootersSite/zeroingmethods.msnw

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