Absolute or Lower 1/3 when cowitnessing?

[Mtbkski]

OK, I'm looking at buying a red dot for the AR. But I got a couple questions about what I should do.

I know I have two choices when mounting the sight. 1) I can set it up for absolute co-witness. 2) I can set it up to 1/3 co-witness.

Which one do you guys prefer? And why do you prefer it set up that way?

In your opinion, what are the advantages to one way over the other?

I included this video for those that may not know what I'm talking about.

[chp1911]

I prefer absolute. I don't see a need to have two different cheek welds on a rifle.Why take muscle memory out of the equation? If you battery goes dead all you have to do if flip up your BUIS and you are back in business.

[Mtbkski]

I prefer absolute. I don't see a need to have two different cheek welds on a rifle.Why take muscle memory out of the equation? If you battery goes dead all you have to do if flip up your BUIS and you are back in business.

But wouldn't the move on of your cheek placement be so suttle that it would barely be noticeable? Yet, the amount of sight that is blocked when sighting absolute, seems to take up an awful lot of the view in the red dot?

I have never really thought about the stock being placed in a different place on my cheek. But it seems that it would be extremely suttle if noticeable at all.

I guess in a "crisis" shooting situation. Even a small movement would make you readjust which would cost you time in trying to shoot rapidly.

[Mtbkski]

I think that this image would support 1/3 over absolute. Yet, most people seem to favor the absolute method.

You would think being able to see clearly and everything in your field of view would be more important.

Since most LaRue red-dot mounts are lower 1/3, we get asked this all the time. The short answer is...it was "by request".
The long explanation is, it's really all about reducing clutter, and always being ready.

Our Aimpoint and EOTech mounts are optimally designed for weapon systems that run with fixed sights or BUIS's deployed in the upright position. Since it takes time to deploy flip-up irons, we here at LaRue (and many instructors) recommend you operate with the irons upright when possible.

Chances are, if you actually need your irons, you're getting pretty busy, with at least one threat occupying your attention. Keeping them up, but out of the way, is the best of both worlds. Our lower-1/3 design keeps those irons out of the way, until they are needed.

Clutter in you field of view (FOV) isn't a good thing...with respect to the popular T1 micro, an upright rear sight can optically cover roughly 50% of the FOV. You can cover the front of an Aimpoint all you want, and still use the sight (keeping both eyes open), but covering the rear obstructs both target and reticle. (see the pic below).

[Mtbkski]

Found this stuff elsewhere. And it really seems to support using 1/3 sighting.

"What about my cheek weld?"
Well...cheek weld is one of the most important factors that provide successful results when precision shooting. Especially when using high-magnification...We make several different mount heights for rifle scopes that keep that issue in mind.

That being said, cheek weld with a non-magnified red-dot optic (like an Aimpoint or an EOTech) is marginally more important than proper cheek weld with an aiming laser. Generally speaking, if you see the reticle, you're operational. Most people find the cheek weld with our mounts for these optics to be more than adequate, and the shift to the lower 1/3 for irons is minimal and intuitive.

Keep in mind, Aimpoints and EOTechs are intended to be used while in a variety of firing positions, many of which have little, or no cheek weld. If you are concentrating on cheek weld too much, you are not using the technology to it's fullest.
Hope all this helps clarify...

Even when you use the lower-1/3 method, the dot can be used "centered" in the tube. When both irons and dot zeroed, you can hit any target you can put the dot on, anywhere in the viewing area...independent of the irons. When you shift your eye position to the irons, the dot will follow (unless you turn the unit off).

As you move your head, and keep the weapon steady, the dot will not move. That's the beauty of a red dot (like Aimpoints and EOTechs). The red dot and the Irons work completely independent of each other.

It's a common misconception that you need to center the red dot and the irons in the viewing area.

[TonyF]

Lower 1/3 is quite popular these days but I still prefer absolute cowitness.

It's there but I doubt a shift in cheek weld would be that significant in the context of forcing one to revert to the BUIS.

The reason I keep using absolute cowitness is that in an emergency, even before deploying the BUIS the ocular lens of (in my case) the aimpoint can be used as a "field expedient" ghost ring and enables me to get hits out to 35 yards. As the situation allows, I can then deploy the BUIS. The advantage is that nothing changes. Not cheek weld, and most importantly, the threat perspective through my sighting system, Red Dot or BUIS, is ALWAYS in the center of the FoV.

The lower 3rd does open up FoV to an extent but [sarcasm] how in the world did anyone ever manage to survive when iron sights were the only option with that HUGE front sight tower and post blocking out so much of the FoV of the rear aperture [/sarcasm]?

IMNSHO, this is yet another example of Col. Cooper's concept of Preoccupation with Incidental Increments.

Bottom line is that it really doesn't matter much which cowitness you choose. Flip a coin.

[TonyF]

Found this stuff elsewhere. And it really seems to support using 1/3 sighting.

Yes it does.

"What about my cheek weld?"
Well...cheek weld is one of the most important factors that provide successful results when precision shooting. Especially when using high-magnification...We make several different mount heights for rifle scopes that keep that issue in mind.

That being said, cheek weld with a non-magnified red-dot optic (like an Aimpoint or an EOTech) is marginally more important than proper cheek weld with an aiming laser. Generally speaking, if you see the reticle, you're operational. Most people find the cheek weld with our mounts for these optics to be more than adequate, and the shift to the lower 1/3 for irons is minimal and intuitive.

Keep in mind, Aimpoints and EOTechs are intended to be used while in a variety of firing positions, many of which have little, or no cheek weld. If you are concentrating on cheek weld too much, you are not using the technology to it's fullest.
Hope all this helps clarify...

Even when you use the lower-1/3 method, the dot can be used "centered" in the tube. When both irons and dot zeroed, you can hit any target you can put the dot on, anywhere in the viewing area...independent of the irons. When you shift your eye position to the irons, the dot will follow (unless you turn the unit off).

The issue is that reflex sights are "supposed to be" parallax free but they aren't. At least not 100%.

It's a common misconception that you need to center the red dot and the irons in the viewing area.

This is true. But with absolute cowitness the threat perspective in my aimpoint ocular lens FoV won't change if my dot disappears because the tip of my front iron sight will always be right there in the same spot as the dot. I will not have to "reacquire" a new sight picture as I would with a lower 1/3 cowitness. Referring to the first image of an aimpoint with a 1/3 cowitness (centered) note that you would not get a CoM hit without adjusting your POA.

I'm not trying to convince anyone to select an absolute cowitness over a 1/3. Just pointing out how ridiculous some of these arguments are that basically amount to nothing on the battlefield.

I'm used to absolute cowitness and I'm not changing for a what I consider to be a "perceived" improvement over absolute cowitness.

[Dochartaigh]

All I'll say about lower 1/3 versus absolute, is do you really want your sights in the way when you're looking at the red-dot with an absolute co-witness? It's always been lower 1/3 for me. Simply makes more sense and takes an extremely small shift to transition from the red-dot to the irons.

Also, I noticed you linked to the video from Primary Arms. If you decide to go with a Primary Arms Micro red-dot (which are very popular and a great deal for the money) please keep in mind that they sit a little higher than a real Aimpoint does. So for instance if you want to have lower 1/3 co-witness with it, you'll need to get an absolute co-witness mount for it (which is lower, and compensates for the P.A. Micro dot being tall than the Aimpoint Micro the mount is really made for).

[Mtbkski]

I'm not trying to convince anyone to select an absolute cowitness over a 1/3. Just pointing out how ridiculous some of these arguments are that basically amount to nothing on the battlefield.

I'm used to absolute cowitness and I'm not changing for a what I consider to be a "perceived" improvement over absolute cowitness.

Exactly why I started this thread. I wanted peoples opinions and thoughts on the subject. Good to hear from those that use it and what they think.

I understand there are pros and cons. But wanted to hear why some people chose what they did. Was it because of "everyone else" or do they have a real reason for using what they do. Always good to hear from you Tony.

[Mtbkski]

Also, I noticed you linked to the video from Primary Arms. If you decide to go with a Primary Arms Micro red-dot (which are very popular and a great deal for the money) please keep in mind that they sit a little higher than a real Aimpoint does. So for instance if you want to have lower 1/3 co-witness with it, you'll need to get an absolute co-witness mount for it (which is lower, and compensates for the P.A. Micro dot being tall than the Aimpoint Micro the mount is really made for).

The one web sight I found them on, actually sells two different sight mounts for them. One designed for absolute and the other for 1/3.

https://www.primaryarms.com/Primary_...se_p/md-07.htm

I think my biggest concern about going with 1/3 is that the red dot will sit to high. Wish I could shoot a couple rifles that had them mounted both ways.