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Thread: Different Reticle cant in LPVOs amongst several uppers

  1. #1
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    Different Reticle cant in LPVOs amongst several uppers

    I often move my LPVOs around from carbine to carbine, mostly in search of what I like best, where. When I mount an LPVO (ADM, Larue or Geissele) I use a plumb bob to get the reticle straight.

    Once I start moving the optic and mount around to different uppers I will notice a slight reticle cant. It’s often so slight I won’t notice it on 1x. In fact, I’ve completed a Kyle Defoor carbine class only to notice a noticeable reticle cant when I come home and do maintenance. Didn’t seem to hinder me out to 200yd on a B-8 during the weekend.

    I feel as if I am tightening the mounts to uppers in a repeatable way and as per manufacturers instructions. Whichever original upper I used to plumb bob align the reticle appears very straight. All other uppers show a slight variance in reticle cant. I am able to hit B/C steel to 500yd no issues. 600yd gets sketch but that’s my skill limitation and usually a slight wind that gets me.

    Does anyone else experience this?

    Seems to me, at 1x it won’t matter much due to using the center of the reticle w/ illumination/dot.

    I probably subconsciously level the reticle when I am in prone or resting on a bag to shoot further.

  2. #2
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    Interesting.....you'd think as long as you were moving the whole thing as an assembly and reattaching mount same way the crosshairs would have same level from upper to upper. Only thing that instantly comes to mind is maybe one has something like an A2 or PRS stock, another something like an MOE & that looser stock allows you to cant the rifle a little & you're not feeling that? Or something else different enough about the rifles - LOP, grip, support hand placement spot, etc - they feel the same shouldered but you're unconsciously canting one?

    Or rifles in same vise showing the change in level from upper to upper?

    Do you have same issue with Geisselle QD mount vs the ADM? Or possibly the Larue depending on type. Reason I ask is I find it MUCH easier to torque the screws mounting an optic in the Geisselle type where the rings are horizontal. I often mess up torquing the rings & have to re-do a couple times when they're vertical like an ADM - I'm not so good with those & have noticed what was dead nuts wasn't any more after the torque wrench.....
    Last edited by CMV; 06-21-19 at 07:36.

  3. #3
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    This is a mount/upper interface issue, there is no way to correct it other than getting upper receivers that are machined exactly the same way, good luck with that. Does point out why it is usually a bad idea to swap optics between uppers.
    “The Trump Doctrine is ‘We’re America, Bitch.’ That’s the Trump Doctrine.”

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  4. #4
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    This is a non-issue until you get out to maybe 750 yards or more in my opinion. If it's that minimal, I'd ignore it.
    "What would a $2,000 Geissele Super Duty do that a $500 PSA door buster on Black Friday couldn't do?" - Stopsign32v

  5. #5
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    Great comments. Occurs in all my ADM LARUE and G mounts. All these carbine are using different stocks (BCM SOPMOD, B5 SOPMOD, B5 Bravo, MAGPUL CTR).
    I have the same struggles with my verticals rings but end up redoing them to where they level after torquing. I agree G mounts are the easiest to level then torque.

  6. #6
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    This is also what I am suspecting. Uppers are BCM Aero Larue and Colt. Even between two BCMs or two Colts I get some can’t unless it goes back on the original upper where I leveled the reticle.

  7. #7
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    Good and practical advice. I seem to level the reticle when zero’ing and shooting on any magnification. Gun still “feels” like it’s up and down. When under the stress of a match or timed drill I don’t notice anything is wrong.

  8. #8
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    I would say don't worry about it.

    What I mean is, you're still hitting what you're aiming at. You completed that class, and didn't even notice. Which is outstanding.

    It's obviously annoying. Only solution is to only leave it on the dedicated upper it was originally "righted" on, or just do what you're doing, and roll with it.

    In the end, all that really matters is that you get consistent hits.

  9. #9
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    Not being a smarty pants here.... check your stock slider-- is it straight up and down with the gun or is the buffer tube canted just a teeny bit?

  10. #10
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    It seems like a rare occurrence when I'm absolutely certain that my reticle is perfectly straight. It hasn't seemed to matter on 5.56 at those distances. On a precision / long range rifle, it is probably more important to get the reticle perfect. I agree with markm that past 750 yards it matters.

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