Why co-witness?  To line the dot, reticle, or triangle with the front site?  Very curious as to why all this attention is being paid to it.

TS

Believe the best reason is to have your irons centered in the viewing area of the red-dot or triangle scope. This way one maximizes the view ya get of the irons should the scope battery fail.

I also find that if I place the red-dot atop the front post, (looking over the rear BUIS) I am assured of a consistent cheek weld and it's like added insurance my POA will be my POI. Much like an accomplished bow-hunter strives for consistency by drawing and holding to the same point each and every time, same principle.

Mike

I maintain my Aimpoints batteries, however, I believe in Murphy.

[i]This is my reply to the same question from this thread in the [b]Optics[/b] forum.

[url]http://www.ar15.com/forums/topic.html?b=3&f=118&t=157407[/url][/i]



First, remember that you use your irons OR your optic, NOT BOTH AT THE SAME TIME.  To do so would defeat the simplicity of using an Aimpoint-type of sight.

Having your Aimpoint and iron sights [b]co-witnessed[/b], allows you to use your iron sights THROUGH your INOPERATIVE optic.

It would be great to have a clear field of view for your optic sight, nothing but "glass".

But whether you can do this depends on how you answer the following question:  [b]"how fast do I need to access my iron sights in the event my optic sight fails"[/b]?

If you have a need to [i]instantly[/i] aim your weapon in the event your optic sight fails, then having your optic and iron sights co-witnessed is essential.  

The trade-off for this capability is having your front sight in your optic field of view when you're using your optic sight.  You will be looking over your rear sight aperture so at least that won't be in the way.


[img]http://www.imagestation.com/picture/sraid59/p2c737bfd262fd05a083e0f206f757178/fc5d0546.jpg[/img]


[i]NOTE:  It was difficult for me to take this picture, and it doesn't depict what I want it to as well as I'd wanted it to.  What I didn't do is focus the camera on the dot, which would've blurred the front sight.[/i]

THE FRONT SIGHT WILL NOT BE THIS CLEAR in actual use.  As you focus on the TARGET, the front sight will "ghost" out to a large degree.

That's the tradeoff that you'll deal with, and not a bad tradeoff at all for the instant sighting capability.  

Notice again that the rear sight aperture is out of the way.

This is the reason for using "spacers", to raise the height of the optic sight.  We try and raise the sight high enough so that we can minimize the obstruction of the front sight assembly in the optic's field of view when we are using the optic as our primary aiming system.

We want to get the front sight assembly as low in the optic's field of view as we can, while still having it visible enough to get a good sight picture, if we have to go to irons.





Okay, the optic FAILS and the optic aiming point DISAPPEARS.  You simply lower your cheekweld SLIGHTLY to look through the rear sight aperture and line up your irons THROUGH the inoperative optic sight, as if the optic sight ISN'T THERE.


[img]http://www.imagestation.com/picture/sraid59/pb43e619a439df4195f30f842c37fbfcc/fc5d0549.jpg[/img]


Chris

About this specific part of your post:



It's a [i]phenomenon[/i] (that's the best word I can think of right now) that when your iron sights and Aimpoint is zeroed for the same distance, THE AIMPOINT IS TURNED ON, and you're sighting THROUGH YOUR IRONS, that the dot will be resting on the tip of the front sight post.

This is because the dot in the Aimpoint "floats".  Regardless of where it's located in the field-of-view, that's where the bullet's going to hit.

To describe this phenomenon in NO WAY implies the use of irons and the Aimpoint together.  

[i]It's just an interesting fact that's good for boresighting or quickly confirming the zero of the Aimpoint in the field, AND THAT'S IT![/i]

So .... you are NOT going to use both TOGETHER when firing your weapon.  That would defeat the purpose of the optic sight.

Either your optic is your primary sight, or your irons are, [b]with your optic either TURNED OFF or inoperative[/b].


Chris

Thanks, that's what I thought.  I guess I won the bet.  So you [b][red]do not have to cowitness when firing on a target[/b][/red].  That's what made sense to me.  If you had to cowitness to use an Aimpoint or EOTech, quick target acquisition (the benefit of said sights) would be lost and irons would work as well.

TS