AR-15 A1 Battle Sight Zero

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Aguila Blanca

Staff
All the articles I've seen on setting a battle sight zero for the AR-15 seem to be based on a 20" rifle with A2 sights. Mine is a 16" carbine with A1 sights. So, no large and small apertures in the rear sight, and no elevation adjustment at the rear sight.

It appears that the two apertures are the same size. One article I found suggests that one is higher than the other, but neither of mine is marked 'L'.

I want to use a 50 yard / 200 yard battle sight zero but how do I determine which aperture to use?

The AR is an Olympic Plinker, vintage approximately 2000 (if that makes a difference).
 
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AK103K

New member
I have an early 70's, Colt SP1, which is basically a M16A1. It has the A1 type rear sight. It does have the flip dual aperture on the rear, and both appear to be the same size. One is marked "L". I cant remember ever seeing one that wasnt marked like that.

If youre simply looking for the 50/200 zero, and both apertures are the same, does it really matter which one you use? Zero the rifle and see how things turn out. If theres a difference, use the one that gives the best results.

50/200 should cover you out to 300 with one hold.
 
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Charlie98

New member
50/200 should cover you out to 300 with one hold.
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That, sort of...

I have my original target from Basic with the A1, the zero ranges are 25M/250M with the 20" -A1, which made it good to 300M without sight or POA adjustments. I suppose with a 16" barrel 25M/200M is probably a better option, but I don't know if it would be good to 300M without POA adjustments.

My target says to use the 'L' aperture to zero, then flip it to the unmarked one. In the absence of that, just use one or the other... and then check the difference between them at 200M to make sure you aren't missing anything.
 
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AK103K

New member
I came across this when I went to zero my AR pistols, and while researching it, everyone seemed to have a different answer and reason as to why.


This makes things a lot clearer. At least to me anyway.....

http://arma-dynamics.com/zero-considerations.html

It covers barrel lengths from 10.5" up to 16" using a couple of different loads.

Has one AK load too.
 
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AK103K

New member
When the "L" sight is up, the L is on the bottom of the sight on the rectangular base, below the aperture.
 
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Bartholomew Roberts

Moderator
The A1 sight should be a 5mm aperture and a 2mm “L” aperture and are basically set up for a 40m/250m zero. If you zero at 50yds with the lower aperture, you should be pretty close.
 
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AK103K

New member
I just checked my SP1, and both the apertures on the rear sight seem to have a 1.7mm aperture. If I measure down from the top of the carry handle to the top of the two sights, the "L" sight is 2.0 mm, the unmarked is 2.3mm. Im thinking that may be a clue.

I did try measuring up from the bottom of the carry handle to the top of the sights, but I wasnt getting consistent measurements for some reason.

The only thing I cant measure accurately is the height of the holes, which seem to be in about the same spot in the rear sight. At least they measure the same from the top of the sight to the top of the hole, so that pretty much makes them the same.

Id try measuring down from across the top of the carry handle and see if you see a difference. At least on mine, the "L" is that 0.3mm higher.

ETA: If this is really bugging you, why dont you just buy one that has has the "L"? :D
 
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Bartholomew Roberts

Moderator
Well, if your sight aperture isn’t L-marked, we are just assuming it is like other A1 apertures - which may or may not be the case given the diversity in AR15 parts.

Easiest way to check is to zero on one aperture at 50 and then flip apertures. If your point of impact goes up, that’s your L-aperture. If it goes down, that’s the unmarked aperture.

Likewise, the long range aperture may not match the A1 trajectory perfectly either if it is some kind of “Island of Misfit Toys” aperture.
 
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raimius

New member
Also realize that the 50/200 zero is an approximation for most 5.56 loads and barrel lengths. It is only true for a specific load and barrel combo. You will need to do actual testing to see how much variance you get (e.g. zero at 50, then test at 200. You can adjust after that, depending on whether you value the near or far zero more, if there is more variance than you want.)
 
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Aguila Blanca

Staff
raimius said:
Also realize that the 50/200 zero is an approximation for most 5.56 loads and barrel lengths. It is only true for a specific load and barrel combo. You will need to do actual testing to see how much variance you get (e.g. zero at 50, then test at 200. You can adjust after that, depending on whether you value the near or far zero more, if there is more variance than you want.)
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That's great in theory, except that the range I usually shoot at is an indoor range that only goes to 25 yards, and doesn't allow centerfire rifle. Ny testing I do is completely dependent on persuading a friend to get me into the outdoor range he belongs to -- which only goes to 100 yards.

I'm looking to zero for XM193, 55-grain ammo. Running the trajectory for that ammo with the MV for a 16" barrel, the 50-yard zero actually does give a 200-yard zero. At 100 yards I should be 1.37 inches above point-of-aim. That's about the best I can do. But I would much prefer not to waste my friend's time going through a bunch of trial and error with two different apertures. Maybe that's what it will have to be, but I would still hope someone can tell me if the 'L' aperture is up when the sight is flipped forward, or back.
 
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AK103K

New member
Its pretty simple to verify while you shoot, as JMR40 and Bartholomew mentioned.

Shoot three, check your group, flip the sight, and see where the next three go.

If you dont plan on shooting beyond 300, does it really matter which you use?

On the A2 sights, I like the 0-50 sight for close up, as its got a larger aperture, and more of a ghost ring to it. But, at least with my aging eyes, the front sight isnt as clear as Id like it for more precise aiming. The smaller, longer-range aperture, cleans that up nicely.

With the A1 sight, unless you drill one out, you get the same aperture for both.

Without doing anything else, six rounds should clear it all up for you though. ;)
 
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pblanc

New member
On all of the A1 rear sights I have seen, when the "L" (long range aperture) is up, the other (short range aperture) is flipped forward toward the muzzle.

Of course, the usual method of zeroing the M16 A1 with M193 55 grain ball ammo was to zero at 25 meters using the L aperture, then flip the rear peep back for a 250 meter battle sight zero with the other aperture. The shorter carbine barrel and lesser muzzle velocity will probably shift your far zero a bit closer than 250 meters.
 
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GarandTd

New member
Slap me now and put me in my place, but can't you just "trial and error" your way in to getting to know our rifle? I'm not trying to insult.....just can't think of any other way to gaurantee your own zero.
 
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GarandTd

New member
Forgive me if I'm over-stepping. I hit the range a couple times a week when I can. If I want to know what my rifle will do, I take it out and test it in different scenarios. That situation give me the best frame of reference, regardless of what other people do or experience.
 
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