Rifle Scopes  Absolute or lower 1/3rd co-witness with aimpoint?

30cal_Fun

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I bought an Aimpoint Comp C3 for my flattop ar15 and I am currently deciding over which height mount I should buy for it.
We don't have as much choice over here in The Netherlands but the best option I have seen is either the American Defense AD-68, which gives an absolute co-witness according to the description, or the American Defense AD-68-H, which should give a lower 1/3rd co-witness.

Which of you (would) prefer an absolute co-witness an who would prefer a lower 1/3rd co-witness with an Aimpoint, and why?

All experiences are much appreciated!
 

RotARy15

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Re: Absolute or lower 1/3rd co-witness with aimpoint?

I voted lower 1/3 just because that is how mine is setup. I also have folding irons.

It really depends on your setup. What iron sights do you have? If the front sight is fixed, then a lower 1/3 would make the sight picture a bit cleaner as the front sight would be less intrusive. If you have a folding front sight then you can stick with absolute because they will be folded out of the way anyway.

The absolute co-witness will make it easier to use your iron sights while viewing through the glass. Whereas the 1/3 will often make it harder to see the bottom 1/4 of the rear sight because the black sight will blend in with the black housing of the optic, which leads to slight inaccuracy.

I went with the lower 1/3 even though I had folding irons simply because I wanted to use the LT129 mount. And I figure, if I ever need to shoot using the irons through the optic, chances are that I haven't had time to hit the quick release mount and drop the dead optic, and because of that I probably won't notice the slight reduction in accuracy because my world is exploding around me.
 

30cal_Fun

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Re: Absolute or lower 1/3rd co-witness with aimpoint?

Thanks for your opinion RotARy15.
And thanks for the excellent link Drifter 1.

I have a fixed front site. I regularly shoot internal competition at my range so I will continue to use the carry handle sight.
I haven't decided on a proper rear sight to use for competition in combination with the aimpoint, so for the coming time the aimpoint will be used instead of the the rear sight.
I am leaning towards the lower 1/3 because my head is not in the upright position when looking through the iron sights, it makes full contact with the stock.
 

BAGunner

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Re: Absolute or lower 1/3rd co-witness with aimpoint?

With my folding front and rear sights, I prefer absolute co-witness. This way I maintain the same cheek weld regardless which sight I use, red dot or iron.

Given a fixed front sight, I will probably go with lower 1/3 just like you.
 

swimmer105

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Re: Absolute or lower 1/3rd co-witness with aimpoint?

I also have front and rear folding sights and prefer absolute co-witness. I like the way everything lines up when you look down the sights.
 

RotARy15

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Re: Absolute or lower 1/3rd co-witness with aimpoint?

I should have mentioned the cheek weld difference.

From my point of view, although there is a notable difference, I find it to not matter too much.

With an Aimpoint, the dot is damn near parallax free. And as such, it is still very usable when placed anywhere in the optic. You could be using a cheek weld identical to the irons and the dot merely moves to the lower 1/3 of the glass. Because the dot doesn't have to be centered in the glass, the difference between absolute and 1/3 isn't that problematic.

My belief is this, your face will never be able to get closer to the bore than it already is. No matter what stock you have on an AR platform, the buffer tube governs the minimum sight over bore and iron sights have been designed with this in mind. Because of this, is see no real personal benefit of absolute co-witness.

Think of it this way, with absolute co-witness there is no way to use the dot below the centerline of the optic because there is no way to get your face lower. This in turn means that if anything changes and forces you to have your head a little bit higher than usual, you are quickly limited by the top of the glass. On the other hand, if you have a 1/3 co-witness, putting your face as low as possible places the dot at the bottom of the glass. If you need to go higher, you have an extra 1/3 of glass above standard.

Simply put, if you can't possibly go lower, why not make that the optics lower usable limit therefore giving you a higher limit in the opposite direction.

Reflex optics are designed to be fast to use, intuitive tools. They naturally do not require precise repeatability of cheek weld. I understand that repeatability is key to mastery of a weapon. If repeatability is important to you, then by all means do so. I built my AR to be a fighting oriented rifle and wanted more tolerance to WTF situations that would force me out of the ordinary.
 

KTDLS7

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Re: Absolute or lower 1/3rd co-witness with aimpoint?

Fixed front meant lower 1/3 for me. If I had folding F&R, probably would have gone with absolute.

Kevin
 

matt2143

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    Re: Absolute or lower 1/3rd co-witness with aimpoint?

    I run a folding set with absolute, I also like having the optic lower to the receiver
     

    Laseredge

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    Re: Absolute or lower 1/3rd co-witness with aimpoint?

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Matt2143</div><div class="ubbcode-body">I run a folding set with absolute, I also like having the optic lower to the receiver </div></div>

    +1
     

    Tangodown911

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    Re: Absolute or lower 1/3rd co-witness with aimpoint?

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: LCJones</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Matt2143</div><div class="ubbcode-body">I run a folding set with absolute, I also like having the optic lower to the receiver </div></div>

    +1 </div></div>

    +2

    This is how I run more than one of my rifles.
     

    One-Eyed Jack

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    Re: Absolute or lower 1/3rd co-witness with aimpoint?

    If your normal cheekweld works with lower 1/3 cowitness, then you have more of the sight picture available for observation and targeting. You can still use your BUIS. However, it may not work for some people.
     

    harbinger

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    Re: Absolute or lower 1/3rd co-witness with aimpoint?

    I run a fixed front sight and folding BUIS rear, absolute co-witness. While it keeps the front sight in the picture when using the red dot, the benifit is that if the dot goes out right when you need it, you just keep the front sight centered in the tube of the red dot and can keep putting fairly accurate rounds downrange until you transition to the back up rear iron.
     

    AvsFan

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    Re: Absolute or lower 1/3rd co-witness with aimpoint?

    It really comes down to personal preference. When I first set-up my EoTech - I started with a 1/3 co-witness w/a YHM riser. For me, I absolutely hated it.

    What I didn't like is deploying my rear BUIS, obtaining a sight picture w/my irons and having the dot above my front sight post. With an absolute - the dot will be directly on top of your front sight post (touching the tip).

    Sold the riser and mounted my EoTech directly to my picatinny rail for an absolute co-witness - Bingo! But, I would suggest trying both to see what your preference is.

    my $0.02
    smirk.gif
     

    Drifter™

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    Re: Absolute or lower 1/3rd co-witness with aimpoint?

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: AvsFan</div><div class="ubbcode-body">

    What I didn't like is deploying my rear BUIS, obtaining a sight picture w/my irons and having the dot above my front sight post. With an absolute - the dot will be directly on top of your front sight post (touching the tip).

    </div></div>

    In my experience, the dot will sit on the front sight post with either setup (Absolute Co-Witness and Lower 1/3) when the correct sight picture with irons is obtained. If a proper sight picture with the optic is obtained instead (with the dot in the center of FOV), then yes, the dot will float above the irons using a Lower 1/3 setup.

    For what it's worth, if I sight in both irons and a T1 optic independently, the dot always appears on the right top edge of the front sight post. One can be used as a rough zero for the other, but my suggestion is to verify both with actual shooting.
     

    Joe Curnarski

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    Re: Absolute or lower 1/3rd co-witness with aimpoint?

    I run an Aimpoint T-1 on my patrol rifle. People whose opinions I trust run with a fixed front post and the folding rear BUIS in the "down" position. They recommend a lower 1/3 co-witness. I also prefer the lower 1/3 co-witness but prefer folding front and rear BUISs because I find having the front site in view with the red dot makes my sight picture too "busy".

    Sorry I digressed there, but I wanted to show that I prefer the red dot and only the red dot in my field of view when I engage. With the sights in the lower 1/3, should the red dot go down, all I need to do is lower my head slightly, flip up the front sight, and use the T-1 as a large ghost-ring. This is accurate at close range if you practice.

    Some postings on other forums make mention of the fact that shooters with absolute co-witness, under stress, try to align the rear sight, the red dot, and the front sight, thereby negating the advantage and purpose of the red dot sight.

    Others may know more though.

    Hope this helps & good luck!!

    Joe
     

    unreconstructed

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    Re: Absolute or lower 1/3rd co-witness with aimpoint?

    I prefer lower 1/3rd so the iron sights are less in the field of view when looking thru the red dot optic. I don't use the iron sights when I have a red dot mounted, but have no problem "dropping down" to use the irons if needed.
     

    Dbltapipsc

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    Re: Absolute or lower 1/3rd co-witness with aimpoint?

    I go with an absolute, folding front and rear with the front left up. when running a t-1, if the optic dies i can use the t-1 tube as my rear aperture.
     

    jerseymike

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    Re: Absolute or lower 1/3rd co-witness with aimpoint?

    1/3, i have troy flip ups but keep them up, if my eotech dies while actually "using" it, I dont have to waste time fiddling with the sights.
     

    11B-B4

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    Re: Absolute or lower 1/3rd co-witness with aimpoint?

    1/3rd I cant stand shit in the way of my sight picture. thats why SOCOM changed the eo-tech out to get over the top of m4 sights.


    Its just much nicer in my opinion, opens up the viewable plane.
     

    HPLLC

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    Re: Absolute or lower 1/3rd co-witness with aimpoint?

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 11B-B4</div><div class="ubbcode-body">1/3rd I cant stand shit in the way of my sight picture. thats why SOCOM changed the eo-tech out to get over the top of m4 sights.


    Its just much nicer in my opinion, opens up the viewable plane. </div></div>

    KUDOS- I don't need shit in my sight plane. They also opted for throwlevers so they don't have to co-whitness - they will just rip the scope off and get rid of that shit in the way too.
     

    shootist~

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    Re: Absolute or lower 1/3rd co-witness with aimpoint?

    I went from a Lower 1/3 with a ML3 to Absolute with an Aimpoint Micro and decided Absolute is my preference. But I'm left eye dominate and have a lower cheek weld than most. The rear BUIS generally stays folded down, but there are no major issues if I leave it up either - whether looking through or above. With my natural cheek wield, the dot appears just a hair above the fixed front sight. Many people prefer the cleaner sight picture from the lower 1/3, but with the focus on the target this is not an issue (for me).

    With the ADM modular system I used with the Micro, you can swap from Absolute to Lower (and vice-versa) for about $20.
     

    SigKev

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    Re: Absolute or lower 1/3rd co-witness with aimpoint?

    Prefer the lower 1/3, as mentioned above I appreciate having the optic less cluttered with the irons.