Eotech 553 - Help Needed!

[Bobby Ricigliano]

Hello CG,

I finally upgraded to an Eotech 553 from the various lesser red dot sights have been using for years.

The Eotech is fantastic and mounts easily with the integrated ARMS throw levers onto my M&P15 rifle.

Since I haven't been to the range yet, I tried to manually line up the reticle with my already zeroed BUIS, a flip up Midwest Industries sight. Besides the fact that the BUIS is barely able to line up with the front sight post through the lower 1/3 of the glass, the reticle disappears completely and cannot be brought up high enough to be visible when using an iron sight picture.

If I disregard the rear sight, the reticle is clear and bright and centered as it should be.

1. Is my BUIS too short?


2. Is the Eotech zero process completely independent of the
BUIS?

[Bobby Ricigliano]

I guess I am confused because my Lucid HD7 optic reticle sat right in the center of an aimed iron sight picture and I thought I could duplicate that with the Eotech. Any help/suggestions/insults are welcome and thanks for reading.

[OpticsPlanet]

The 553, being on a 7mm riser due to the quick release, is not intended to provide an absolute co-witness. I assume that's what you're going for when you say "I tried to manually line up the reticle with my already zeroed BUIS".

Mark H.

[Omega13device]

If you zero the irons and the optic at the same distance then the dot in the reticle will sit atop the front sight post when you align the irons. But you're not required to do it that way, and in practice you don't use your Eotech while looking through your irons. Part of the value of an RDS is that eye alignment is irrelevant. Just put the dot on the target and fire. It doesn't matter where the reticle is within the optic window.

[EvolutionGSR]

Do you have a vise, or something to hold the rifle still? Get it stationary, aim thru irons at a point on the wall. Mark the wall if u can. Raise your head to see thru eotech, adjust eotech to same point on wall. That should get U on paper at 25 to 50 yards to do fine adjustments at the range.

[Bobby Ricigliano]

I am processing all of this good advice here. Thanks gentlemen. I gather from what I have read, here and elsewhere, that you can have a lower 1/3 iron sight picture through the glass, while the optic reticle may sit elsewhere, but still be zeroed as well when using the reticle only. In other words, the irons are zeroed, and the reticle is zeroed, but may be independent of each other?

[SuperSet]

Yes, zero both independently.

[krisjon]

I am processing all of this good advice here. Thanks gentlemen. I gather from what I have read, here and elsewhere, that you can have a lower 1/3 iron sight picture through the glass, while the optic reticle may sit elsewhere, but still be zeroed as well when using the reticle only. In other words, the irons are zeroed, and the reticle is zeroed, but may be independent of each other?

Yes. That's how 1/3 co-witness works. You're on a built-in riser with that model Eotech, so you shouldn't try to be positioning the reticle to sit atop the front sight post (which is absolute co-witness). A lot of people (including myself), prefer 1/3 because it gives you an unobstructed sight view of the Eotech reticle. Zero each independently and you're good to go.

[Bobby Ricigliano]

Solid copy to all responders. I mechanically zeroed the Eotech per the manual and will be live fire sighting it in Monday. Many thanks to all who took the time to respond

[Omega13device]

Yes. That's how 1/3 co-witness works. You're on a built-in riser with that model Eotech, so you shouldn't try to be positioning the reticle to sit atop the front sight post (which is absolute co-witness). A lot of people (including myself), prefer 1/3 because it gives you an unobstructed sight view of the Eotech reticle. Zero each independently and you're good to go.

NO.

If you zero your irons and optic at the same distance and then look through the irons, the dot will ALWAYS sit on top of the front sight. This is true whether you use absolute or lower 1/3.

Absolute vs. lower 1/3 just refers to WHERE the irons line up within the optic window. For absolute they line up in the center, for lower 1/3 they line up in the lower 1/3.

Absolute - irons line up in the center of the window. Not great if you use fixed irons, because they take up a lot of space in the window. Works better with flip-up sights.


Lower 1/3 - better for use with fixed sights because they're mostly out of the way, and it's not hard to look over the top of them (see next pic).


Looking over the top of the sights with lower 1/3 (center image.

[nitroxdiver]

Agree completely with above ^ post.

[negolien]

sigh

The 553, being on a 7mm riser due to the quick release, is not intended to provide an absolute co-witness. I assume that's what you're going for when you say "I tried to manually line up the reticle with my already zeroed BUIS".

Mark H.

Yup.... Not all the HWS do 100% co-witness like my XPS That pictures crap because the irons are on two differant planes. Optics is correct.