1/3 Co-Witness or Absolute?

[Nostinkin]

My next purchase for my new 15-22 is a Primary Arms Red Microdot sight that sells for $89.99 with an AR base that goes for $29.00 for either the 1/3 or absolute co-witness, that is either choice cost the same amount of money.

I've a fair amount of experience shooting, mostly iron sights, but I'm not that well versed in co-witness particulars. Since I've got the the Magpul iron sights, I thought I'd try to educate myself with such things.

What do you guys say: Go 1/3 or Absolute?

Or, yank the Magpul iron sights and forget about co-witness all together.

If I go that route, (which will look a lot cleaner and very slightly reduce weight) which base would be the best bet for height?

If I recall correctly, the absolute base is 1.5" high and the 1/3 is described as 'Lower 1/3 - 1.65' - which presumably means the 1/3 is .15 higher than absolute co-witness base.

What say you?

 

[sithlord]

I tend to prefer absolute, as it represents a consistent cheek weld.

I also have my BUIS off most of the time. As a result, it is possible that I don't really have an absolute OR a lower 1/3.

I have a Vortex StrikeFire I on one, and it comes with the riser. On another, I have an inexpensive reflex sight on a .83" UTG riser IIRC. Both allow comfortable cheek welds.

 

[Nostinkin]

sithlord,

"I also have my BUIS off most of the time. As a result, it is possible that I don't really have an absolute OR a lower 1/3."

Thanks for your response. I need mucho education about co-witnessing. Sounds a little like religion...

Anyway, I'm a bit confused as I thought to have co-witness as part of the equation (if you will) you have to have the BUIS installed. Am I wrong about that?

 

[sithlord]

A co-witness describes the pairing of the BUIS and a non-magnified optic (red dot). However, to achieve that, you are really referring to how high the riser is for your red dot.

Just because I don't have the BUIS on, or they aren't flipped up, doesn't mean that they aren't in a particular co-witness; if installed and flipped up, they WILL be co-witnessed. Whether that is absolute or 1/3 or something else, matters not to me.

It's kinda like saying you have a vehicle that CAN be a 4 wheel drive vehicle, but because the road conditions never require it, you stay in 2WD mode. You wouldn't refer to the vehicle as a 2WD, but rather a 4WD vehicle.

Of course, that's just my humble opinion. Others may be a bit more pedantic and require that both aiming devices be 'active' for it to be called co-witness.

In the image below, it shows the difference between an absolute co-witness and a lower 1/3 co-witness. The red dot always shows point of aim, regardless of where the head position is. However, it aligns with the BUIS depending on head position.

If the red-dot is always point of aim, unless your front/rear sights are fixed (as traditional M4's, etc are), then why even use the BUIS (except for electronics/battery failure)? Some competitions may require use of BUIS over red dot or other optics. In which case, they are easy to install, confirm that they are sighted in (turn on the red dot), then remove the red dot..

I hope this helps.

Cheers!

 

[Nostinkin]

sithlord,

Thank you sir!

Very informative.

If your patience with my questions is still up to it: It looks like Absolute C. would not allow as quick a red dot target acquisition compared to 1/3. In other words A.C. looks to me as if the iron sights kinda/sorta crowd the red dot, therefore I'd find the red dot quicker with a 1/3 cowitness due to the separation from the front iron sight.

Is my speculation roughly accurate?

Or, as I suggested in an earlier posted yank the iron sights and simply have no crowding of the red dot.

 

[sithlord]

If you have flip down BUIS, I'd flip them down or take them off. I learned on iron sights, and the red dot feels like cheating by comparison.

In a battle rifle scenario, I can see pros and cons in both, which would be why both are offered. With absolute co-witness, your cheek weld doesn't change if the optic goes out.

If it REALLY concerns you, they also make 45 degree offset BUIS. You keep the cheek weld, but rotate the firearm 45 degrees to use the BUIS.

Ultimately, since you've already purchased everything, try it in all combos (AC, 1/3, no irons). It's not like you are committed to one way in perpetuity.

Cheers!

 

[Nostinkin]

sithlord,

Thanks again, much appreicated.

 

[Biggfoot44]

Here's some more input -

If the gun has fold down sights front and rear, and you customarily keep them folded down and use the red dot as primary sight, then no potential downside to absolute cowitness.

If one or more iron sights is fixed, or you prefer to default have the irons up and usable, then many people would prefer the lower 1/3 .

 

[Gamer]

I have setups in absolute and lower 1/3. I prefer absolute with rear sights that fold, red dot top of the front post. Have a 6940 with fold down front. Very clean sight picture. I like the clean pov so much I'm thinking of doing offset backup sights on another.

 

[medic15al]

With non-folding BUIS like the Daniel Defense A1.5 the lower 1/3 co-witness is the superior choice as you can see the target surroundings better in event of multiple targets. The stand up irons would conceal or obstruct that.

With fold down sight such as Magpul either would be fine as when the BUIS is down the red dot is unobscured.

 

[Jayclimber]

I'm with Gamer on this one! I have a fixed front iron and fold down rear that is absolute co-witnessed with my red dot setup! I like having identical cheek welds for irons with red dot and having the dot sit on top of my front post just feels more natural for target acquisition! But go with whatever setup feels best and you shoot best with! What works for one of us doesn't necessarily work for someone else!

 

[MichiganScott]

I also vote for absolute co-witness. I find the lower 1/3 confusing when trying to get off a quick shot. The circle within a circle of the absolute cowitness is very similar to the sight picture used by 50 meter (and other) small bore competitors. They use a target with a X-ring smaller than the diameter of a .22 bullet and consistently clean the target. Your eye will automatically align the rings concentrically without any conscious effort on your part.

 

[Nostinkin]

After much deliberation, I ended up buying a: Sun Optics 23X33Mm Reflex Sight/Red/Green/IR/4-Reticle CD13-RRG

It comes with a base that may (or not) do an a.c. we'll see...

The overall reviews give it high marks.

For a total of $119.99 delivered, I'm sure it'll do an adequate (and I hope better than adequate) job. If not, it won't break the bank.

Next up: Perhaps, an ALG trigger. The stock trigger isn't bad, but I'm spoiled. All my 5.56 cal AR's have Geissele triggers. While the ALG isn't comparable, it's still better than stock.

My wife calls my AR's my "Barbies" because I'm always adding or subtracting something on them.

P.S. For the first time yesterday between showers, I ran 80 flawless rounds through the 15-22. Not a single hiccup. For the most part, I was shooting M-22 Winchesters. I started off with 6 CCI's and they shot without a problem, but I wanted to try these M-22 and they performed beautifully.