Explanation of Co-Witness

[2011BLDR]

An optic that is mounted up higher allows for ones head to be more upright giving superior performance in the following areas:
Better Situational Awareness
Less helmet shift that interferes with vision and sighting
Less neck strain from having the helmet and NVG’s tilted off center
Overall better balance and smother movement

Optics are the primary and in some unit’s the 2nd back up. If the primary is a 1.?-4X of some kind (TR21, Short Dot, NF…) the CQB dot (M68, EoTec, MRD) is the secondary and the Irons are the last resort . If the optic goes down, the operator can still shoot using the window, silhouette of the optic or a top adjustment knob as a reference point to aide in alignment until he can remove the optic and go to a secondary optic before being reduced to the irons.

The advantage of the optic is in reducing the number of things in the sight picture down to 2 ( retical & Target) from 3 ( Rear sight , Front sight & target). The “absolute co witness “ is a step back wards as you now have 4 things in the sight picture (Rear sight , Front sight retical & target).

Out,
2011BLDR

[Mojo58]

...so after this thread, I'm picturing a Vodka ad: Absolut Co-Witness

Too bad I have no Photoshop skills.

LOL

[SinnFéinM1911]

the utility of a 'absolute/true' co-witness, IMHO, is as a sanity check to see if anything has shifted, or checking that you optic is still zeroed when you remove and replace it. the dot doesn't have to be co-zero'd with the irons to do that - you can zero the dot independantly, then check to see where it is in relation to the front sight when looking through the irons (windage should be centered, but you can be 'one dot width' above the FSP, etc).

normally, you'd never look through the irons when using the dot. i agree - it defeats the purpose. however, there have been instances where i HAVE utilized the rear aperture with the dot to sharpen it up. the sharpness of the dot depends mostly on your vision. my eyesight isn't that good, and using the small rear aperture when sighting in the dot, or for longer ranges on small targets acts like almost like a pinhole camera and sharpens up a dot that might appear a bit blur or fuzzy. for those with less than perfect vision, look at your dot, then flip up the rear sight with the small apreture and look through it again. chances are you'll see a sharper, more distinct dot.

i think the point of brett's original post was to try to get some agreement/standardization on the terms used. here are my suggestions for defining the terms:
Co-witness - the ability to view the irons sights through the tube. This applies to any height of the optic relative to the irons, as long as they can be seen. the dot can be adjusted to the irons or zero'd independantly.
Co-zero'd - i suggest discarding the terms 'absolute' or 'true' co-witness as they're confusing. this is when the dot is adjusted so it sits on top of the FSP when looking through the irons. the zero will only be valid for the distance they're both zero'd at.

I sat back and thought about this over the weekend over many, many pints of Guinness and using the term "Co-Zero", if your BUIS or Sight already sit in thee bottom 1/3 of your Optic / Red Dot, and your BZO your Optic /Red Dot @ 25m, and then adjust your Sights to it, your will not have a correct 300m BZO. Or even the other way around.

Lets just say that you sight in your Optic / Red Dot @ 25m and then adjust your Irons to them. Well then look at the setting on your elevation, it will be way blown out due to the fact that you (from the start with your lower 1/3 co-witness) have a gross adjustment of coming up at .25" or more. Then after your Rear is at the correct level, bringing your front sight post up to Co-Zero would be almost to the point of your Front Sight Post and Detent coming out or damn close to it.

IF your sights are on the same level with a Co-Axis with the plan of each being the same plan, it would be close or if not perfect for the idea of Co-Zero to work.


And going back to another question that was brought up earlier (sorry for hi-jacking my own thread). There is DIFFERENT POA/POI for different Optics / Red Dots with many variables in place, ammo types, optics, bbl lengths, etc. Example: Say you sight a EOTech in @ 25m (and the offset is 1.25 low) and your think that your POA/POI in Center mass of the Black Dot or Circle and your zero it to that. Then push your 25m BZO to 300m and see what happens. IF you were at center mass on that @ 300m your will be aprox. 15” High, and that is in perfect conditions taking out all accountable errors, IE MOA of ammo and the aprox 1 MOA for shooter added to the MOA of the gun. In all reality your could be pushing to a extreme of almost 30” off your center mass BZO @ 25m. Hope that makes sense !


B

[rob_s]

Wow, I have to say I'm amazed that this discussion has actually gone on for three pages. I never would have thought this would have ganered even 1/20th of the attention.

[SinnFéinM1911]

Wow, I have to say I'm amazed that this discussion has actually gone on for three pages. I never would have thought this would have ganered even 1/20th of the attention.

ARE YOU SAYING MY TOPICS ARE DUMB !

jk

[rob_s]

ARE YOU SAYING MY TOPICS ARE DUMB !

jk

no, but....

I think that everyone is going to have their own way of doing things, and as long as what they're doing works for them and they made an informed decision about their way then it's all good. I understand the need to all be on the same page, but topics like this have a tendency to become nothing more than semantics.

I just got done with a three day carbine class where I shot a 3x mini-ACOG for two days and an ML2 for the last day. Co-Witness wasn't even an option for me on the first two days.

[SinnFéinM1911]

no, but....

I think that everyone is going to have their own way of doing things, and as long as what they're doing works for them and they made an informed decision about their way then it's all good. I understand the need to all be on the same page, but topics like this have a tendency to become nothing more than semantics.

I just got done with a three day carbine class where I shot a 3x mini-ACOG for two days and an ML2 for the last day. Co-Witness wasn't even an option for me on the first two days.

Well, it is kinda of hard to view any kind of Sights or BUIS though any magnifed optics .

I was pretty much just trying ot make a point that people refer to it many times in reference to "WHY" they purchuse sights or certain mounts for Optices or Red Dots, when most of the they dont really know what they are looking for.

And ot mutulply the problem IF you force a Co-Witness with all you WILL NOT have a correct 200 or 300 m BZO.

[rob_s]

I was pretty much just trying ot make a point that people refer to it many times in reference to "WHY" they purchuse sights or certain mounts for Optices or Red Dots, when most of the they dont really know what they are looking for.

Very good point, and really it carries over into the whole entire idustry. This is the thing that keeps TOS going, in fact.

And ot mutulply the problem IF you force a Co-Witness with all you WILL NOT have a correct 200 or 300 m BZO.

This is why I prefer to zero both seperately and see where everything winds up.

[militarymoron]

Lets just say that you sight in your Optic / Red Dot @ 25m and then adjust your Irons to them. Well then look at the setting on your elevation, it will be way blown out due to the fact that you (from the start with your lower 1/3 co-witness) have a gross adjustment of coming up at .25" or more. Then after your Rear is at the correct level, bringing your front sight post up to Co-Zero would be almost to the point of your Front Sight Post and Detent coming out or damn close to it.
B

LOL - sometimes semantics are fun to discuss, too. actually, discussing semantics assumes that your already have a basic understanding of the discussion and are digging for deeper understanding and definition. on TOS, it's just 'what's co-witnessing?' instead of delving into the nuances. i find this discussion refreshing as i can learn more, and maybe identify my own misconceptions.
but since brett asked the original question, i do see merit in having the terms clearly defined/standardized, especially when it comes to military RFPs/contracts etc. and hey, what else would i do on my lunch break?

brett, in the above situation, the elevation of the irons won't be 'blown-out', because you're not trying to bring up the irons to the height of the center of the optic, just adjusting the irons so they coincide with the dot when looking through them. the dot is parallex free, so it 'moves' down in the vertical plane to the level of the irons when you look at them. if someone wants the optic irons centered in the optic (like if they wanted to use the front sight and optic tube as a large ghost ring as someone else mentioned above), they'd just get a lower mount.

[SinnFéinM1911]

If you have a elevation drum on your rear, your would have to be almost at 500m to reach the red dot center, so it could not be a true 300 m BZO.

What if your engagment is at say 550m, how would you adjust ?