how do you zero dual aperture rear sights

[mac1911]

http://www.midwayusa.com/viewproduct/?productnumber=467794

My friend asked me to help him zero his AR. he has these installed. I replaced my dual apature rear sight on my aR with a scope before I even tried the flip up sights.

@ 25 yards it shot very low from point of aim. windage was ok. I adjusted the front sight until point of impact was same as point of aim. The rear aperture was marked 0-200 and large peep hole. the flipside of the aperture was much smaller assume for greater distance.

Now at 100yards the rifle was shooting very high aprox 16" with the 0-200 peep?

what am I missing with this sight set up?

 

[RichM]

When zeroing, always use the smaller aperture.

ETA: The sight picture should be the same regardless of which aperture is used. The tip of the front sight should be centered in the peep.

The larger aperture is needed at night or when wearing the chemical protective mask because you have difficulty seeing through the smaller peep sight. You also use it at close distance to improve your situational awareness and to allow for the parallax difference between sight alignment and barrel alignment.

 

[vellnueve]

I zero with the small aperture. The MI rear uses the standard A2 setup and thus the apertures are not in the same plane.

 

[Andy in NH]

For most standard AR iron sights, the large aperture and the small aperture are not on the same plane; you'll get a different POI by flipping between apertures. Even the action of flipping the sight on the windage screw will cause a horizontal POI change.

XS sights has a "same plane" aftermarket sight to correct this problem:
AR-15 and M16 TACTICAL SIGHTS

AR-15/M-16: Rear Sight Elevation Shifts and the need for a Same Plane Aperture Sight

As originally designed the AR-15/M-16 sight system adjusts for windage at the rear assembly and for elevation in the front to zero the rifle to the individual shooter. To obtain the ballistic adjustment needed for longer range shooting the original rear sight had one aperture higher than the other. While this system would not give the shooter an exact elevation adjustment for a specific range, it would under battle conditions put the bullet close enough for government work so to speak.

The new A2 rifles and carbines employ a rear sight system that includes a range cam to allow the shooter to more precisely adjust the ballistic arc to their needs. This system eliminated the need for an elevation shift between the large close quarters aperture and the smaller long-range aperture. However the aperture shift is still with us today.

Comparing some of the rear sights available today there appears to be 3 variations available. The 1st style (and oldest) has a .014 offset. This gives a 2.52 inch shift in point of impact at 100 yards between the two apertures. The 2nd style has a .017 offset, which shifts point of impact 3.06 inches at 100 yards. The 3rd style has a .024 offset giving a 4.36 inch shift in P.O.I.
All of the points of impact shifts shown above are for the standard barrel AR-15/M-16 that has a sight radius of 20 inches. The shorter sight radius (14.5 inches) of the M4 carbine and weapons of similar configuration increase the amount of point of impact shift. The shifts for these shorter sight radius weapons are 3.48, 4.25, 5.96 inches respectively.

The only reason for the various shifts would be for changes in the ammunition used by the military over the course of this weapons employment.

Most people are completely unaware of this elevation change that occurs when the aperture is shifted from one to the other. They just figure that their rifle is doing something strange.

Our aperture sight for this weapon has both the large and small apertures on the same plane so there is no difference in the point of impact when you shift from one to the other. We have also offset one of the apertures by .007 to make up for the sideways movement of the aperture on the windage screw as it pivots.
By installing our same plane rear aperture you now can sight in your rifle using the smaller aperture and shift back and forth between the two apertures as your light and range needs change without having to do mental gymnastics to know where your bullets impact will be.

 

[andy t]

You are missing the understanding of trajectory. You ended up creating a zero close to the 25m/300m that the army uses. However, there are many better options available. Personally I use the 50 yard zerot. It can be achieved either by shooting POA/POI at 50 yards or by having your POI around 1.5" lower the POA at 25 yards. This will give you the following trajectory:
distance - impact point
25 yards - 1.5" below
50 yards - same
100 yards - 1" above
220 yards - same
after about 220", the bullet will be falling.
Another popular alternative is the 100 yard zero, to achieve wich you want POA/POI to be the same at 100 yards or POI to be about 2" low at 25yards.

Personally, I only use the large aperture on my iron sights since they are all relegated to the "backup" role, with a red dot being the primary sighting device.

http://www.midwayusa.com/viewproduct/?productnumber=467794

My friend asked me to help him zero his AR. he has these installed. I replaced my dual apature rear sight on my aR with a scope before I even tried the flip up sights.

@ 25 yards it shot very low from point of aim. windage was ok. I adjusted the front sight until point of impact was same as point of aim. The rear aperture was marked 0-200 and large peep hole. the flipside of the aperture was much smaller assume for greater distance.

Now at 100yards the rifle was shooting very high aprox 16" with the 0-200 peep?

what am I missing with this sight set up?

 

[Viper22]

This method is what I used to zero my AR. http://www.ar15.com/forums/topic.html?b=3&f=18&t=328143

 

[op4guy]

You are missing the understanding of trajectory. You ended up creating a zero close to the 25m/300m that the army uses. However, there are many better options available. Personally I use the 50 yard zerot..

I too run a 50/200 zero. For nearly 20 years I have used the 25/300 zero but after my last carbine course I thought I would give it a try. Once you get it dialed in you are pretty darn good from 25-300 without any major changes.

I totally understand why the Army uses the 25/300 zero though. It is simple and the close target helps those who can't really shoot. I can't tell you how many people I have seen struggle to zero at 25 yards...50 would have been a disaster!

 

[mac1911]

I was a tad confused. We set the rear sight to the larger 0-300 peephole. @ 25m it was shooting a tad low and left. I lowered the front until we where hitting the center or point of aim. The adjusted windage on rear sight to the right. OK 25m good little groups POA=POI
now out @ 100m it was hitting about 16" high? windage was decent.

 

[Harleynut]

I had seen "The rifleman" show how to do the Army zero in on youtube. Here is his link its in two parts. http://www.youtube.com/user/TheRiflemanChannel#p/u/29/MrDzwFMRFSM
I would think if you followed that procedure and started shooting out 600 yards that the guns that were calibrated for 556 should be closer then if you were to do the same using 223.

 

[Len-2A Training]

Check out this newly revised Top Post for LTC Chuck Santose's Improved Battlesight Zero instructions.

http://www.northeastshooters.com/vb...ttlesight-Zero-for-the-M4-Carbine-M16A2-Rifle

 

[mac1911]

What was really getting me is why it was shooting so high @ 100. If it was a few inches I would have passed it off as "it is what it is". We where useing Fed XM193. I have the same sights that came with my AR. I recently reinstalled and will paly with the added info provided on my next trip to the range with my AR

 

[andy t]

I would think if you followed that procedure and started shooting out 600 yards that the guns that were calibrated for 556 should be closer then if you were to do the same using 223.

It's 5.56mm and .223 remington. You don't calibrate. You "zero". Usually you want to stick to the same brand/type and even the same lot (if high precision is desired) of ammo. So obviously zeroing for one type and shooting another type of ammo would yield different results at 600 yards.

 

[mac1911]

http://www.youtube.com/watch?v=Etnf76QTu_U&feature=related heres one of the better videos I found. The problem being for me is all these AR BZ sight ins are for standard AR/M16 rear sight with elevation adjustment. I was looking for more on the particular sight I have in the OP. Im not looking for clover leafs on the bulls eye. Just a good chance to hit the kill zone.

I will play with the info and the sight again soon.