I have my EOTech 512 mounted with an ARMS #40L-SP BUIS. Now, I have just finished putting this rifle together and haven't taken it to the range yet. However, when looking through the sights, I notice that, when cowitnessing, the EOTech circle is off to the left of the front sight when I use the BUIS to sight through. Shouldn't the EOTech reticle be right over the front sight?

Do you have the same cheek weld as you do when you use your irons?  Also, if you haven't taken it to the range, the sight might be off because you haven't sighted it in yet.

When I flip up the rear BUIS, and sight through it, the EOTech reticle is sitting just off to the left of the front sight.  I'll try to get to the range soon and sight both of them in and see where they are then. Thanks!

Quoted: I have my EOTech 512 mounted with an ARMS #40L-SP BUIS. Now, I have just finished putting this rifle together and haven't taken it to the range yet. However, when looking through the sights, I notice that, when cowitnessing, the EOTech circle is off to the left of the front sight when I use the BUIS to sight through. Shouldn't the EOTech reticle be right over the front sight?

I had the same issue until I brought it to the range and sighted the eotech in, now the reticle center dot is on the tip of the front sight post .

PocketG: Thanks for the info.

Quoted: PocketG: Thanks for the info.

I like EOtech a lot, I practiced and practiced my butt off with it. I can't shoot without it now. I like competing with Aimpoint  users.

I have just finished putting this rifle together and haven't taken it to the range yet.


Then how can you expect them to co-witness?

If either the BUIS or the Eotech is sighted in, then you can adjust the other sight so they both co-witness.  

Go to the range, get the Eotech sighted in first.

Then adjust the BUIS (and front post) so that when looking through the irons, the center dot of the Eotech appears to be right on the tip of the front post.

Then turn off the Eotech, and fine tune the iron sights.

---

Or you can do the opposite, leave the Eotech off, sight in the iron sights.  Then turn on the Eotech, and adjust the Eotech so that the dot appears to be on the tip of the front post when looking through the BUIS.  Then flip the BUIS out of the way, and fine tune the Eotech.

This whole idea of using one zero'd "system" to establish the zero of the other is about the laziest thing I keep reading about on this site.

Why is it so difficult to just take the time to zero them separately?  My EOTech and Irons were zero'd on their own, first at 50 yards, then at 200 yards.

When returning to the 50 yard line, I was rewarded with EOTech and Iron sight groups that coincided perfectly.  5 shots using each overlaid into a single, quite decent group of 10.

Given that the EOTech reticle moves around the view when your eye moves, why is even reasonable to expect "eyeballing" the two systems together would give a precise result?

Paladin