Does your BUIS aperature block out the dot when your cowitnessing if your eye is in the wrong place or does the small ring fade out so that the reticle is never blocked.  I know the 65 moa ring of an eotech would prolly always be visible, but its 1 moa dot and Aimpoints 4 moa dot are what I am worried about.

is there any difference in the effect between the small and the large reticle if this happens?

The BUIS is for backup, not for co-witnessing, although you could do that if you wish. Best thing is to fold down the BUIS and just use the EOtech. If the EOtech fails, THEN use the BUIS. If your using a removable BUIS, remove it until you need it.

Quoted: Does your BUIS aperature block out the dot when your cowitnessing if your eye is in the wrong place or does the small ring fade out so that the reticle is never blocked.  I know the 65 moa ring of an eotech would prolly always be visible, but its 1 moa dot and Aimpoints 4 moa dot are what I am worried about. is there any difference in the effect between the small and the large reticle if this happens?

Another person who is missing the idea.  When you have a paralax free optic cowitnessedd with the irons you are supposed to look over the top of the BUIS to view the dot.  You only look through the rear aperture when you are actually using the irons.

I was thining more of a fixed BUIS that stays on all the time.  I dont think the BUIS should EVER leave the gun.  With and ARMS 40 etc there is no trouble, but If you can cowitness without loosing your dot behind the aperature, I would decide on something like a chopped carry handle instead or Larue or Cavarms BUIS.  

Quoted: Quoted: Does your BUIS aperature block out the dot when your cowitnessing if your eye is in the wrong place or does the small ring fade out so that the reticle is never blocked.  I know the 65 moa ring of an eotech would prolly always be visible, but its 1 moa dot and Aimpoints 4 moa dot are what I am worried about. is there any difference in the effect between the small and the large reticle if this happens? Another person who is missing the idea.  When you have a paralax free optic cowitnessedd with the irons you are supposed to look over the top of the BUIS to view the dot.  You only look through the rear aperture when you are actually using the irons.

Yeah I know, but I just want to know if either aperature blocks the dot from sight.  Im considering an Eotech directly on the rail and i know the Irons will be sitting right in the middle of its screen.  If it does then I might up to the Larue Eotech mount or just go Aimpoint with the extensions.  Only a few more month (wife permitting) till I get the funds for such.

Im confused on what your trying to ask. Will the dot be blocked by the apature? Yes, if you move your head. The whole idea behind the EOtech is you can move your head anywhere and as long as you see the dot, the bullet will go there. With co-witnessing, you have to have everything lined up to see the dot. The bigger apature will give you more head movement.

I dang sorry guys I just realized what your saying..Yes I already knew you were supposed to look over the dot.   Sorrry for the misunderstanding.

I just want to know If the dot can be easily blocked completely from sight so I could decide whether I wanted to raise the optics so the Irons are in the bottom 1/3rd of the optics or if having them half way up was ok

Quoted: I dang sorry guys I just realized what your saying..Yes I already knew you were supposed to look over the dot.   Sorrry for the misunderstanding.

Part of the misunderstanding may be your use of terms.  The aperture is the hole in the rear iron sight.  The dot is the aiming point in the optic.  You look over the top of the aperture.  You look at the dot.

I just want to know If the dot can be easily blocked completely from sight so I could decide whether I wanted to raise the optics so the Irons are in the bottom 1/3rd of the optics or if having them half way up was ok

\
This part is personal preference.  Some people don't mind having the dot just above the rear aperture and some want the dot higher above the reticle.  There is a little bit of trade off there.  Getting the optic a little higher means the view of the dot is better but it also means that you have less of a view when using the iron sights if the optic is not removed.

In either case, the dot shouldn't be blocked when you're looking over the rear sight.  If the rear sight blocks the dot then you obviously are not looking above the rear sight.  It doesn't matter whether you select the large or the small aperture hole because you don't look through the hole.

i've always said that you are much faster with the aimpoint with a flip-up BUIS... such as the troy or GG&G

Quoted: i've always said that you are much faster with the aimpoint with a flip-up BUIS... such as the troy or GG&G

+1