Explanation of Co-Witness

[M193 BALL]

Choice A is the definition I use.

I do the zeroing backwards from you guys. I zero with irons, then put the dot on top of the front sight post, almost like a boresight. I then shoot just optics to verify or set the optic to shoot same POA/POI as the irons.

THATS WHAT I DID back in 2001

I think its a great way

Zero IRONS @ 50 yards

Put ML2 dot on the FSB Post

Then zero from there

wich only takes a few shots

also did my 551 that way




Works Great at my Local range since it only goes 200 yards another 20 yards to the Berm

Chuck & Forest help me out alot back then

[tiger seven]

Co-Witness is -

A - Having the ability to be able to align your Iron Sights or BUIS through your Optics / Red dots (where it locates in the glass it does not matter {middle / bottom 1/3}), leaving your red dot Zeroed.

B - Sighting in your Optics / Red Dots and then bringing your Iron Sights or BUIS to align with the Red Dots.

Option A is what I refer to when I use the term "co-witness." It just means that you can align your front and rear iron sights though the optic, should the optic fail, eliminating the need to remove it in order to transition to irons. Normally, the irons would sit in the lower 1/3 of the FOV.

Option B is something I have heard referred to as "absolute co-witness" in order to distinguish it from Option A.

Like Erick said, my dot (or reticle) is where it is and my irons are where they are, because they are different systems. I zero the two separately. If I'm using an optic (in my case an EOTech + LaRue mount) the iron sights might as well be invisible to me. I should be seeing only on the reticle and the target. If I am using irons, the optic is either off the weapon or inoperable, so there is no reticle in my FOV. That approach seems to work for me, but I have limited experience and am a long way from being an expert. If I am mistaken or misinformed, please let me know.

Derek

[mattjmcd]

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?

Thanks.

[KevinB]

You could.

However if you run the irons in the lower 1/3rd if you drop your head intothe irons -- the dot will co-witness provided you use the same zero.

[Robb Jensen]

With Aimpoints I zero the irons and then zero the optic. The optic on the rifle can be shot by looking over the irons and putting the reticle where you want the bullet to go (faster) or going lower on the stock and lining it up in the lower 1/3 (slower).

I like it higher because it's faster.

Some competition guys (like Daniel Horner and Ernest Langdon) run the very tall LaRue SPR scope mounts with S&B Short Dot scopes (the ones for mounting behind PEQ-2s) because they're a little faster than the standard 1.5s or SPR-Es because you don't have to get as low on the stock.

[Tim_W]

I am building a 12" SBR. I am having trouble deciding on fixed or flip up BUIS for Co witnessing in the lower 1/3 of the sight picture. The optic will be a EO-Tech 553 or M3 with 4 moa dot. I have just read Pat Rogers latest article on red dot optics their proper uses in the Gun Rag and it has put me on the fence on this. I understand the negatives of having fixed centered Co witness site that was already out. What would you consider the best choice of the two, fixed 1/3 co witness or flip up centered or 1/3 co witnessed.

If going fixed it would be a LaRue rear BUIS with a standard pinned FSB or for the flips a set of Troy flip BUIS. This will be for a CQB and defensive gun, also the one I will use in classes such as Pats. It will be run hard by your definition Pat. It will be dirty far more than it will ever be clean. It will only be used with a zero magnification optic such as the two listed.

Which would give me the the best results in reliability and performance? Have any found a decrease in acquisition performance and speed with the fixed lower 1/3 co wit sites because of partial loss of that part of the site picture?

Do you know if the LaRue BUIS and FSB will Co wit to the lower 1/3 on the Aim point and the EO-Tech? Can they be made to with the proper LaRue mount? If so which. If it matters the hand guard will be a DD 9.5" FSB to a LaRue Upper.

Pat if you could weight in on this also I would appreciate your insight. By the way I tried to send you and IM on this question and it kicked it back because you're box is over full just an FYI.

Thank you in advance for taking the time to help.

Tim

ETA: I have tried sights both ways and they both seem to work well for me. I would give the edge to the fixed in transition speed. But I just don't know if others have found any deficiencies for having them fixed in the sight picture even if in the lower 1/3.

[Robb Jensen]

The rear sight height is the same regardless of which BUIS you have. The co-witness height is regulated by the optic and or mount. A 553 will co-witness in the lower 1/3. A 552 will if you use a LaRue EOTech mount.

[Tim_W]

What about the M3? Any preference to which you prefer fixed or flip in your goto gun.

Tim

[Robb Jensen]

What about the M3? Any preference to which you prefer fixed or flip in your goto gun.

Tim

Personally I prefer fixed rear sights like the LaRue or LMT. For a lower 1/3 co-witness for an M3 either get the LaRue LT150 mount a ADM AD-68H.

[Tim_W]

Thank you for the information. I am leaning towards the fixed at this point. Moving parts I think are just one more thing that can/will break or stop working when its needed.

Tim