Hello everyone...i'm still somewhat new to the AR15 and all of it's great accessories. I've seen a lot of threads here that mention "co-witnessing" and I was wondering what exactly that means? Does it mean the reticle of the scope lines up perfectly with the front iron sight or what?

Thanks.

Quoted: Hello everyone...i'm still somewhat new to the AR15 and all of it's great accessories. I've seen a lot of threads here that mention "co-witnessing" and I was wondering what exactly that means? Does it mean the reticle of the scope lines up perfectly with the front iron sight or what? Thanks.

Yep, that's it. And talk of it doesn't stop you from having a "Eureka!" moment when you pop a red dot optic on an upper and it lines right up with the front sight...

Ok, that's what i figured. I just wanted to be sure.

So would an EOTech scope automatically co-witness with the front sight just by mounting it on the flat-top reciever?

Bingo -

You can only cowitness non magnified dot type optics, not scopes... not even 1X scopes.

Quoted: Ok, that's what i figured. I just wanted to be sure. So would an EOTech scope automatically co-witness with the front sight just by mounting it on the flat-top reciever?

Automatically? I don't know about every situation - but mine did.

FYI,  I've heard of one other definition of co-witnessing.  It involves the iron sights being visible through the bottom third of the optic's window but they DO NOT align with the red dot.  

That way they don't restrict your field of view through the optic.  But are accessible (visible) without removing the optic.

Mine are all set up to align WITH the iron sights but supposedly the real warriors prefer the second approach.  I cannot argue with that.

height=8

Quoted: height=8 Quoted: Ok, that's what i figured. I just wanted to be sure. So would an EOTech scope automatically co-witness with the front sight just by mounting it on the flat-top reciever? Automatically? I don't know about every situation - but mine did.

So if they don't quite line up you'll have to adjust the reticle a bit?

Quoted: FYI,  I've heard of one other difinition of cowitnessing.  It involves the iron sights being visible through the bottom third of the optic's window but they DO NOT align with the red dot.   That way they don't restrict your field of view through the optic.  But are accessible (visible) without removing the optic. Mine are all set up to align WITH the iron sights but supposedly the real warriors prefer the second approach.  I cannot argue with that.

How can that be co-witnessed then? It's not aligned... the definition of Co-Witness is that the sight is aligned with the irons...?

Quoted: Quoted: Quoted: Ok, that's what i figured. I just wanted to be sure. So would an EOTech scope automatically co-witness with the front sight just by mounting it on the flat-top reciever? Automatically? I don't know about every situation - but mine did. So if they don't quite line up you'll have to adjust the reticle a bit?

Yes, you'll have to adjust the reticle for elevation or windage. It's very easy to do on the EOtech (I assume it's easy on the Aimpoint as well, I've just never done it)... Just bring a regular screwdriver or a quarter with you to the range and you're golden. Or start it at home, drop the optic on and look directly through the center of the window... if your irons are aligned with the dot, great, if not... adjust.

The way I've heard it is "Absolute" co-witness is when the reticle is aligned with the irons.

Use a 1/4" riser under the EOTech, and you get a "1/3" cowitness - irons are still visible, but in the lower third of the window.

As far as sighting an EOTech in (absolute cowitness), what I did was make sure my irons were sighted in, then turn on the EOTech and adjust it to line up with the front post while sighting through both the rear and front irons. (If you just try to adjust the EO against only the front irons you'll go mad and it won't work). Then flip down your irons and you should be good to go, or at least really close.

Quoted: Quoted: FYI,  I've heard of one other difinition of cowitnessing.  It involves the iron sights being visible through the bottom third of the optic's window but they DO NOT align with the red dot.   That way they don't restrict your field of view through the optic.  But are accessible (visible) without removing the optic. Mine are all set up to align WITH the iron sights but supposedly the real warriors prefer the second approach.  I cannot argue with that. How can that be co-witnessed then? It's not aligned... the definition of Co-Witness is that the sight is aligned with the irons...?

No.  Mike is correct.  Both are cowitness setups.

Cowitness just means that you can use the iron sights while looking through the optic.  It does not matter where the irons line up with respect to the center of the optic, as long as you can see from the rear sight to the front sight through the optic.

Note, however, that regardless of where you place the irons when cowitnessing, as long as both the irons and optics are zeroed to the same point you will see the red dot aligned with the tip of the front sight post when sighting through the rear sight.


ETA - Read the first post of The big bad BUIS FAQ tacked at the top of this forum:

What is co-witness? A: Co-Witness is the ability of your irons to look through your optic (1x - not magnified) - so they both shoot on the same trajectory.  There are two kinds - absolute (both the dot and irons are on the same plan), and offset (where the irons are usually in the lower 1/3 of the optics display).  With co-witnessed sights you can verify the zero of the optic by looking through the irons (the dot should sit on top of the front sight).  However, normally you look over the irons and just use the optic (trust me, you won't notice the iron sights); should the batteries fail your head comes down a fraction of an inch and you're using the iron sights (looking throught the now-dead optic). (from the Maryland AR15 Shooters FAQ)

OK I'd never heard of "offset cowitnessing". (I've heard of it aligning in the lower 1/3rd of the window, just not referred to as "cowitnessing")

It's kind of a funny term, no? Like "This dryness is very moist" or something.

Wow....lots of interesting info here. lol. I think i'm good to go though. Thanks to everyone for their input.

Quoted: It's kind of a funny term, no? Like "This dryness is very moist" or something.

The term does create a fair amount of confusion.  I suspect that people think cowitness = iron sights line up with optic's dot.  And that is true.  But it isn't the whole truth.  People forget that with a red-dot 1x optic, the dot is on target regardless of where it appears in the optic's field of view.

Thus you can cowitness with the irons right smack dab in the center of the optic, with them below center, or even with them left, right or above center if you really wanted to.  Of course, I don't recommend cowitnessing with the irons left, right or above center of the optic.

By the way, if you didn't view the link to the Maryland AR-15 Shooter's Site, here is the picture they use to demonstrate various forms of cowitnessing:

So....without looking through the rear-sight, the round with go where the dot is even though the dot is NOT on top of the front sight post?

Quoted: So....without looking through the rear-sight, the round with go where the dot is even though the dot is NOT on top of the front sight post?

Correct.  That is the beauty of a 1x red-dot optic.

ETA - Think of it this way:  If you start out looking through the iron sights, everything is lined up - the iron sights, the red-dot, and the target.  Now, without moving the rifle, move your head up so you are looking over top of the iron sights.  

The front sight post will no longer be on the target because you are looking above it.  But the red-dot sight keeps the red-dot on the target.  And since you haven't moved the rifle, it is still aimed at the same point and the bullet will still hit the target.  

A red-dot sight acts somewhat like a laser sight, except that a laser sight puts an actual beam of light on the target, while a red-dot sight projects an image of a dot so that it appears to be on the target.  In either case, when you see the dot on the target, you know that the rifle is aimed correctly, regardless of where your head is in relation to the rifle.

Wow. Ok. lol. Ya learn something new everday.

Quoted: Wow. Ok. lol. Ya learn something new everday.

See my edited post above your last post.  I added some more information that might be helpful to you.

Oh ok. I'm gettin it now. lol.

Something to keep in mind about co witness sights.  

The old set up on my work gun allowed co witnessing of the optic and irons via a gooseneck mount.  It was always very satisfying being able to pull up to ensure my optic was still lined up after riding around in the car.  Last winter we were at a barricaded gunman and i was working my way up to the residence.  While making my way to the residence I went under a pine tree that had fresh snow on it.  While negotiating the tree a big clump of snow came down and hit me and my rifle.  The mf'ing under my breath due to the snow going down my neck turned into a OH CRAP when I looked at my optic.  The snow was pretty packed into the optic.  I used my finger to get the snow out.  With all the moisture and condensation on the optic it was nearly useless.  I treat all my optics with anti fog cloths too.   I couldn't see my front sight through the optic.  Luckily, things worked out with the gunman.  I was able to remove the sight from my rifle before getting into position - that time I had the luxury of time.  Next time, maybe not.  I was still faced with the dilemma of my rifles sights / optics.  The best I could come up with so far is to mount an Aimpoint on top of the carry handle.  If the snow or whatever decides to make my optic momentarily unusable, I'll still have access to my irons - that is if the sight channel doesn't get plugged up with snow.  Hopefully,  blowing through the sight "trough" would clear it up so I'd have my irons.  

I guess  you folks with flat tops probably use some type of quick release mount and could remove the optic pretty quick.  I'm mandated to carry the A2.  So those of you that have to carry the A2 and like to co witness, my experience may be something to take into consideration.  

Hello to all.
You all just answered a few questions I had too.
I'm a Newbie to AR and picking up good stuff.

Quoted: I guess  you folks with flat tops probably use some type of quick release mount and could remove the optic pretty quick.  I'm mandated to carry the A2.  So those of you that have to carry the A2 and like to co witness, my experience may be something to take into consideration.

Henny, does your gooseneck have weaver rails in front where the optic mounts?  If so, I imagine you should be able to get a quick-release weaver mount for the Aimpoint.  Then when a scenario such as you described happens, you can quickly remove the Aimpoint from the gooseneck but not have to bother fighting to get the gooseneck itself off.

Aimpoint actually sells a set of mounts to do just that.  See here at SWFA.

I don't know how good the Aimpoint quick-release ring mount is, since most people don't think too higly of Aimpoint's standard low ring mount, but even if it isn't the best quality, you may be able to get a LaRue mount to serve the same purpose.

ETA - Here is the LaRue mount I was thinking of.  It is designed for a RAS II, so it is shorter than the standard Aimpoint mount.  Maybe it is low enough to work with your setup.  I don't know, but perhaps someone can do some measurements to find out.

Quoted: Hello to all. You all just answered a few questions I had too. I'm a Newbie to AR and picking up good stuff.

Hi Mechanic.  Welcome to the forums.  You can learn a lot just by reading, but don't be afraid to ask questions as well.

Quoted: Quoted: I guess  you folks with flat tops probably use some type of quick release mount and could remove the optic pretty quick.  I'm mandated to carry the A2.  So those of you that have to carry the A2 and like to co witness, my experience may be something to take into consideration. Henny, does your gooseneck have weaver rails in front where the optic mounts?  If so, I imagine you should be able to get a quick-release weaver mount for the Aimpoint.  Then when a scenario such as you described happens, you can quickly remove the Aimpoint from the gooseneck but not have to bother fighting to get the gooseneck itself off. Aimpoint actually sells a set of mounts to do just that.  See here at SWFA. I don't know how good the Aimpoint quick-release ring mount is, since most people don't think too higly of Aimpoint's standard low ring mount, but even if it isn't the best quality, you may be able to get a LaRue mount to serve the same purpose. ETA - Here is the LaRue mount I was thinking of.  It is designed for a RAS II, so it is shorter than the standard Aimpoint mount.  Maybe it is low enough to work with your setup.  I don't know, but perhaps someone can do some measurements to find out.

zrxc77,

Thanks for the input.  I've been doing quite a bit of training with my rifle set up the way it is now and I feel pretty comfortable with it.  I might not have the co witness that at one time was comforting,  but I find that if I pick an object 50 or so yards away, line it up with my irons, then pop my head up and see if the dot is there, that's more than likely good enough.  If I think it's way off, I'll just use the irons.  With all the bumping and vibrations that my rifle gets, it's still dead nuts on.

Quoted: Thanks for the input.  I've been doing quite a bit of training with my rifle set up the way it is now and I feel pretty comfortable with it.

That's what counts.  And I suspect that the mount on top of the carry handle is more solid and makes for a better balanced rifle.  

Quoted: www.ar15.com/forums/topic.html?b=3&f=18&t=280593

Good thread.  Thanks.

This boggling!!!!!!!!

The objective here is to have  BUISights,  a Back Up Iron Sight.....

On my set ups, I never use the dot and irons at the same time.....

I set the EOTech and/or the Aimpoint up to be on at 50 yards and when I am working with the BUIS, the dot is turned of....

The BUIS is also set to be on at 50 yards, sighted in, red dot off

Remember the good ole geometry lesson,  the more points the more infinite the combinations of lines and planes

Just as it is intended to be, BUIS, back up in the event of a main optic dot failure.

I could care less where the dot is with respect to the sights.

The dots on these holographic sights have a parallax corrective coefficent out to infinity, so when the dot is used with a fixed front post sight, you can move your eyes around and get the post off of the front sight....try it

It just so happmens, on all of my set ups with ARMS and Aimpoints, the front and rear BUIS is in the lower third of the Aimpoint glass, when the rear is depolyed.

With my EOT mounted to the rail, no riser, the BUIS is in the middle of the glass....

But I do not care, the BUIS is used with the dot off....

You will waste a lot of ammo trying to satisfy two masters....we argue about this at the range all of the time and I finally have my shooting buddies conveinced and on my side.

I may be wrong, but this is my logic.  BUIS, used when a back up is needed-no power

77Bronc

Dot on, dot off, BUIS only, whatever,...

I shoot the same way all the time - my positions are independant of the sighting system used.  I place my head on the stock the same way all the time.  

The only question is, which sight do I use?

The red dots are FASTER than the irons.  I use that first, if it's on.  If it's off, I refocus to the front sight and use that.  It doesn't matter.  

Honestly, probably from training, I prefer the irons.  Even so, the red dot is faster - no doubt about that.

A BUIS is used when the primary (non-back-up) sight is INOP.

If your primary site is INOP, there are 2 possibilites:

1.  Primary site INOP, but you can still see through it (dead battery, etc.)
2.  Primary site INOP, you can not still see through it (broken glass, bent, etc.)

Therefore the ability to co-witness only solves 50% of Primary site failures.

A quick-release mount on your Primary site solves 100% of Primary site failures.

IMO a quick-release mount, with practice, is more important than co-witness.

YMMV

Quoted: A BUIS is used when the primary (non-back-up) sight is INOP. If your primary site is INOP, there are 2 possibilites: 1.  Primary site INOP, but you can still see through it (dead battery, etc.) 2.  Primary site INOP, you can not still see through it (broken glass, bent, etc.) Therefore the ability to co-witness only solves 50% of Primary site failures. A quick-release mount on your Primary site solves 100% of Primary site failures. IMO a quick-release mount, with practice, is more important than co-witness. YMMV

Good point. Always good to have a back-up for the back-up.

Nathan

First, zero your rifle with the irons.  

Then, while looking through your irons, adjust the red dot until it is on top of the front sight post.  Your red dot sight should now also be zeroed.

Cpt and Gul,

Good points, all of my optics have some sort of quick release....if total failure due to glass breakage or cannot see thru occurs, the BUIS will be useless until the optic is removed.

The point I was trying to make is the BUIS is there and to be used with the optic turned off, battery failure, dot failure or totally removed.

One guy at the range one day was cursing because he was fighting the dot and BUIS and I told him to quit....relax, turn the damn optic off and then sight in the BUIS...

Bronc