There seems to be a lot of debate as to whether an “absolute” co-witness (as Dick S. used to call it) is the preferred version of the co-witness.
Most of us I think prefer a bottom 1/3 co-witness simply for the reason that it keeps more of your irons out of your FOV. I think people sometimes forget that the optic is the PRIMARY sighting system and the irons are the secondary.
To make it even more interesting, I have even seen some Tier 1 weapons that did NOT co-witness at all (on purpose). The thought was that an optic that is mounted up higher allows for ones head to be more upright giving better Situational Awareness. If the optic goes down, the operator can still point shoot until he can remove the optic and go to the irons.
I have been practicing this recently, by removing my optic and just using my front sight base (no rear) to shoot human size targets out to 75yds! It is VERY easy to do and am fairly confident that I could keep someones head down at much longer distances.
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).
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 !
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.
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.
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.
brett, guess i’m not understanding why you’d adjust the iron sights any different than normal since you’re not trying to put them in the center of the tube. if you sight in the dot at 25M, and the irons at 25M, when you look through the irons, the dot will be very close to being on top of the front sight, even with a lower third co-witness.
If someone is looking for the “Co-Zero” meaning Irons aligned with Optics / Red Dots, and they sight there Optics / Red Dot and then try to adjust thier Irons to the Optics / Red Dot (and they use a lower 1/3 co-witness) they will have a min. of 1/4 inch just to start. A inch in Sight Elevation is ALOT to be moving a Rear Sight to have “Co-Zero”. Did I clear it up ?
What I have used and taught for the last 20+ years for the 5.56MM system on Active Duty, as separate stand alone evolutions:
Iron sights BZO @ 1000” ( 27YD /25M) this will match up 200M with a 20” barrel and 300M with a 14.5”
Verify and fine tune Iron sights BZO @ 200M or 300M as applicable for barrel length
Verify Iron sight POI vs. POA at the following distances 3M 10M 15M 25M 30M 40M 50M 75M 100M 125M 150M 175M 200 M225M 250M 275M 300M and any additional distances that ranges will support, shooter learns hold under and over as applicable to the ranges.
CQB Optics BZO @ 50M
-Verify CQB Optics POI vs. POA at the following distances 3M 10M 15M 25M 30M 40M 50M 75M 100M 125M 150M 175M 200M 225M 250M 275M 300M and any additional distances that ranges will support, shooter learns hold under and over as applicable to the ranges.
Magnified optics BZO @ 50M for things without a BDC ( TR21, CQT….) 100M for BDC equipped optics ( Short Dot, ACOG……)
-Verify Magnified Optics ( without a BDC ) POI vs. POA at the following distances 3M 10M 15M 25M 30M 40M 50M 75M 100M 125M 150M 175M 200M 225M 250M 275M 300M and any additional distances that ranges will support, shooter learns hold under ,over and exact long distance match up range as applicable.
-Verify Magnified Optics ( with a BDC ) POI vs. POA against the BDC at the following distances 3M 10M 15M 25M 30M 40M 50M 75M 100M 125M 150M 175M 200M 225M 250M 275M 300M and any additional distances that ranges will support, shooter learns exact margin of error in the BDC for them selves and the hold over under for the ranges closer than 100M as applicable.
I consider the "absolute co-witness” as Co-Alignment and the bottom 1/3 as Co-Witness.
Whenever possible I try to talk anyone out of using either and using the higher mounted optic to support a heads up shooting position and lower profile fold down iron sights for the reason I posted before.
Out,
2011BLDR
For the guys who run an optic with the reticle above the irons, I have the following question-
Do you use a different zero for the optic? I am not sure if this makes sense, or if it’s even a factor, but I wonder if it can be done? I currently run an EOTech with an absolute cowitness, and the irons are set to the battlesight zero advocated by TriCon/JG in his book. So the zero is the same for both.
If you placed the optic higher, using the lower-third view so often described here, could you set the optic’s zero for a longer range zero? If you COULD do it, WOULD you? Does this even make sense as a question?
LOL:o
