Question about EOtech sight problem

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I have a Colt LE6940 (integral top rail) and an EOTech EXPS2 Holographic Sight with a EOTech 3X Magnifier (optics came as a set). I bought the rifle and optics new last year and I've shot very few rounds with it - maybe 200 or 300 rounds or so. Whenever I went to my range, the wind was pretty strong so I didn't expect sighting to be spot-on but I did notice a potential problem. Today I went to the range and, for the first time, there was almost no wind so I could finally see if there was a problem or if it was just a wind problem before.

A couple weeks ago, I roughly sighted in the rifle at 25 yards knowing where the POI should be for a final sighting at 50 yards. When that was done and the shots were virtually in the same hole, I moved to the 50 yard range. To my surprise, POI was a couple inches to the right. But on that day, there were winds of about 10 MPH to 15 MPH or so and I didn't give it much thought. I zeroed for 50 yards and called it a day. (That should just about zero me at 200 yards too.)

Today I went back to the 50 yard range to check things because I had dismounted and re-mounted the sight to clean the rifle since the last time I was at the range. If I remember correctly, that could throw POI off by 1 or 2 MOA according to EOTech. The rifle was shooting about 1 - 1.5" inch or so to the left now and I assumed that was just from remounting the optic. So I got it zeroed again so the shots were dead on and then moved to the 100 yard range where I expected POI to be about 1.6 high or so. Elevation was good and as I expected but hits were about 1.5" to the right.

After a little thought and after talking to my son who is a precision long-range shooter and ex-Marine (I know - there are no ex-Marines! :)), I realized that this could happen if the optic was aligned at a slight angle on the horizontal axis. I hope that makes sense. If that is the case, then I could expect to always see impacts to the right as I move out to longer ranges if my thinking is correct.

Has anyone seen this before and, if so, what's the fix? If the EOTech is at an angle, is there a way to adjust it? (BTW, my EOTech is quick-release.)

Also, I should mention that I didn't change any adjustments until sighting the rifle. EOTech says the optic is set at mechanical zero from the factory and not to mess with that before mounting it to the rifle so I didn't. I just thought I would mention that. I'm not even sure if that could cause the problem I'm seeing if I had messed with it but I didn't anyway. I mention that because, if it could cause the problem I'm seeing, I could set the optic to mechanical zero again and start over but that shouldn't be necessary if it was zeroed from the factory.

(I would appreciate it if nobody gets into what the best range to sight in is. That's an entirely different issue and it would side-track my question. )

Also, keep in mind that the Colt LE6940 has an integral rail that is part of the upper so there's no issue of the rail being mounted incorrectly.
 
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I'm not seeing where there's any problem with the sights, since you've made continuous adjustments and they seem to be working.

Try adjusting for the range actually you intend to shoot, and concentrate more on your shooting consistancy
 
Snyper,

But there definitely is a problem. I thought my detailed question made that clear. It could be summarized by saying that, when my windage is adjusted correctly at a given distance, hits will be far to the right when I move to a longer distance on a windless day. Then I can adjust the windage so hits are dead-on at that distance but then hits are to the right when I move out to an even longer distance. The wind was dead still. Not even a blade lf long grass was moving.

I also that I had another experienced shooter shoot groups with me and they got the same results. This has nothing to do with consistency on my part. as suggested. Also, I was zeroing another rifle yesterday and had no such problems with that one.

As for consistency, my groups at 50 yard were no larger than a nickel with the exception of one flier. In fact, two groups were literally in the same hole and the hole was still round. At 100 yards, groups averaged about the size of a quarter. Again, I only mention this to avoid having this thread get side-tracked. That's why I was very detailed in my original question. The problem is simply that windage has to be adjusted at different ranges on a dead still day. That's not right. Or to put it a different way, each distance requires a different windage adjustment and, remember, these are short distances.

The only thing I can think of that could cause this would be for the sight to be slightly cocked (not parallel) to the barrel on the horizontal axis. In fact, my son who is a precision shooter, has seen this before but with scopes and suggested that it could be the problem. After thinking about it and drawing it out on paper, it would explain the problem.

I'm a little confused about where you got the idea that everything was working well. You shouldn't have to change windage when you change distances on a windless day. But I do appreciate your response. If this was normal, I would have to have to adjust both the elevation AND windage for every different distance even on a windless days. Nope! Something is definitely wrong. Also, I don't just shoot at one distance and distances are not always known. I could compensate by making windage adjustments or compensating with Kentucky Windage if just shooting targets but I shouldn't have to do that if things are right.

I apologize for my long question but I wanted to be specific and anticipate any recommendations that wouldn't apply. Too many times, threads get thrown completely off track and I wanted to avoid that by being detailed and specific. Apparently I didn't succeed. I thought I described the problem in detail - maybe too much detail. :-)

Anyone else have any ideas?

BTW, I should have mentioned that the rifle was held firmly in a commercial adjustable rifle rest and the trigger is a Giessele Hi-speed National Match Trigger with the DMR spring set so second stage pull is very light and I use great care when zeroing. I mention that so you know that these tests were shot under carefully controlled conditions and another shooter got the same results. This is not an issue of consistency or trigger technique as suggested. I should have also mentioned that the same groups shot with the iron sights didn't have this problem. The problem seems obvious. I'm looking for someone who may have experienced a similar problem and how they fixed it. I may have to send the EOTech back to the manufacturer as I see no possible external adjustments to the EOtech QD base.
 
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Did you adjust the brightness between the two ranges?

The reason I ask is that depending on the brightness, my LEDs will "bloom" and there will be two distinct aiming points. If the same point is not used at both ranges, there will be a shift. I have anti reflective coatings on my glasses and that does help but the problem does not really go away. Just a thought.
 
It could be summarized by saying that, when my windage is adjusted correctly at a given distance, hits will be far to the right when I move to a longer distance on a windless day. Then I can adjust the windage so hits are dead-on at that distance but then hits are to the right when I move out to an even longer distance. The wind was dead still. Not even a blade lf long grass was moving.
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Set the sights for the longest distance and I suspect you won't see a big difference at shorter ranges

If even if the sights were a little crooked, once they are set they shouldn't change since you're not having to align two points

Something else is causing it to shoot to one side

I'm a little confused about where you got the idea that everything was working well.
Click to expand...

I got that impression because you shot groups on different days under different conditions and even removed the sight at least once and were still hitting close to the aimpoint.

Take the gun out of the rest and shoot it normally off sandbags to see if things change
 
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