New to red dot optics - Eotech XPS2-0 questions

[Shao]

OK... so I broke down and bought an Eotech XPS2-0. I've always been an iron sights kinda guy but I gave in after playing with a friend's... I finished building up a lower last night and stuck a BCM middy with C4 rail on it. I've never shot it so I've never had a chance to zero it in.

So.. I get the XPS in the mail today and when I mount it to the top of my receiver, I notice that the reticle is WAYYYYYY off the to the right - noticeably off-center and hanging far off the edge of the rail.

I read in the manual and it says that it should come close to zero from the factory - I know nothing comes zeroed from the factory, but I figured from their explanation that it would at least be close -problem one.

Problem two - I decide to bust out my faithful boresighter. I know that the boresighter works because my only truly zeroed AR is my Sig M400 and the boresighter and trips to the range have proven that. So when I pop in the boresighter - sure enough - it's far off to the right.. like really really far. I adjust it to be in line with the boresighter, inserting and reinserting the boresighter a few times as I always do to eliminate the boresighter being off from the equation.

So... I know that you shouldn't zero in your BUIS by using your optic, but I'm set up right now for an absolute co-witness - so I figured I'd look through the old MBUS sights and see how everything lined up. Not good. To get them to cowitness, I had to move the MBUS windage so that it's noticeably far over to the left. About halfway between the second and third mark. I double checked with the boresighter and the irons lined up with the boresighter...

So... My questions are:

1. Has anyone ever had an Eotech from the factory that far off zero?

and...

2. Has anyone ever had an MBUS rear sight that you needed to move over that far to zero?

Before anyone asks - It's a factory assembled BCM upper and both the MBUS and Eotech are properly installed... any yes, I inserted, turned, and re-inserted the boresight about 100 times trying to fault it instead of the Eotech or MBUS...

[Failure2Stop]

Have you zeroed the MBUS?
If not, you are several carts ahead of your horses.

Typos brought to you via Tapatalk and autocorrect.

[mattg1024]

I always zero by back up sights first. Then when you add a RDS you can eyeball it pretty close with the back ups then fine tune from there.

[Hmac]

Hard to figure out what you're doing, or even parse out what the problem is.

• [1.] Zero your iron sights (I realize theyr'e actually polymer)
  [2.] Mount your XPS2
  [3.] Flip up your now-zeroed sights
  [4.] Turn the XPS2 on
  [5.] sight down your iron sights lining them up as you would to shoot at something
  [6.] Note where the center dot is on your Eotech reticle
  [7.] use the windage and elevation screws on the Eotech to move that center reticle dot right down to the tip of your front sight while sighting through them. it doesn't matter in the slightest whether you're set up for absolute or lower-third co-witness
  [8.] if you can't get enough windage or elevation to get the dot on top of your front sight blade, then the EXPS is broken and you should send it to Eotech to get it fixed
  [9.] You could return the optic to where you bought it, but Eotech customer service is excellent and you might very well get the problem fixed quicker going through Eotech
  [10.] If you can get the red dot to sit on top of the front sight blade with an appropriate number of clicks on windage of elevation left, then flip your MBUS down and go to the range and do final zero on the Eotech. Leave the iron sights alone. Leave them flipped down. You don't sight through them while using an RDS (you may know this, it's kind of surprising how many people don't)
  [11.] Dont forget that an RDS is used with the backup sights retracted. The back up sights have nothing to do with the Eotech.
  

[Shao]

Well thanks for the advice guys... no my irons are not zeroed yet as it's a brand new build and I haven't had a chance to take it to the range. I guess it'll have to wait until Sunday. I just thought that it was odd that Eotech would include info saying that it should be close to zero from the factory and that mine was hanging so far off to the right. I figured the laser boresighter would be a pretty good indicator since it lines up with the sights on my Sig, which is zeroed as perfectly as I can get it - but I suppose that isn't the case? All I know is that this XPS rocks! I don't want to become dependant on it though. For now, it's just an expensive toy until it proves itself to me. I can't wait to get to the range tomorrow and sight it in. Hopefully I didn't get a lemon.

[ra2bach]

Well thanks for the advice guys... no my irons are not zeroed yet as it's a brand new build and I haven't had a chance to take it to the range. I guess it'll have to wait until Sunday. I just thought that it was odd that Eotech would include info saying that it should be close to zero from the factory and that mine was hanging so far off to the right. I figured the laser boresighter would be a pretty good indicator since it lines up with the sights on my Sig, which is zeroed as perfectly as I can get it - but I suppose that isn't the case? All I know is that this XPS rocks! I don't want to become dependant on it though. For now, it's just an expensive toy until it proves itself to me. I can't wait to get to the range tomorrow and sight it in. Hopefully I didn't get a lemon.

wait, you haven't shot this yet? how can you tell your reticle is way off to the right?

the way this sight works is it will stay on target but appear to move around in the hosing depending on where you position your head - check it by getting behind the sight and move your head off your normal cheekweld up and side to side. the reticle should move around inside the window.

is it not doing that? if not, then somethings fubar'd...

[Shao]

wait, you haven't shot this yet? how can you tell your reticle is way off to the right?

the way this sight works is it will stay on target but appear to move around in the hosing depending on where you position your head - check it by getting behind the sight and move your head off your normal cheekweld up and side to side. the reticle should move around inside the window.

is it not doing that? if not, then somethings fubar'd...

Yeah, I mean with a regular cheek weld, it came from the factory looking like the reticle was hanging over the rail. It wasn't parallax or anything. I mean, from just about any angle that you looked through it, it was faaaaaaaar right. I don't need to shoot it to know that it was off. The laser boresight seemed to confirm it. I boresighted the MBUS and the XPS separately, and then they co-witnessed perfectly, but the MBUS windage is way far left. I was just trying to get some insight so that maybe I can save some ammo at the range getting it zeroed.

[Hmac]

Windage for the iron sights "way far left" is usually associated with some canting of your FSB, which in turn is usually due the barrel turning a little within the Limits f the index pin when torquing down the barrel nut. Not uncommon. It has nothing to do with the Eotech, of course.

[skydivr]

I zeroed mine the other day...not off by that much about 12 clicks...at 25 meters..top left was first shot group. Bottom left was confirming..

[Shao]

Windage for the iron sights "way far left" is usually associated with some canting of your FSB, which in turn is usually due the barrel turning a little within the Limits f the index pin when torquing down the barrel nut. Not uncommon. It has nothing to do with the Eotech, of course.

No FSB - MBUS front and rear on a 12" C4 rail... Unless the C4 rail is canted... I don't see that happening from BCM though - you never know...