Rifle Scopes Question re: optic set-up

RHutch

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  • Apr 23, 2005
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    Frisco, TX
    Scenario:

    New rifle, new base, known reliable scope.

    Scope mounted on a flat base (custom base ordered as 0 cant).
    Consistently hits 6" low at 100yds with the elevation in scope maxed.

    I have used this scope on a flat base on two other rifles with success.
    WTH am I missing here? Drivin me nutz...

    ETA: For gigles, I adjusted the scope DOWN and fired a couple rounds. It tracked properly.
     
    Re: Question re: optic set-up

    Quick pics

    IMG_5994.jpg

    IMG_5996.jpg

    IMG_5995.jpg

    IMG_5997.jpg
     
    Re: Question re: optic set-up

    The pic does give that effect.
    If it was angled up, I wouldnt have this problem.
    I may have an issue of getting down to a 100 yard zero...right?
     
    Re: Question re: optic set-up

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RHutch</div><div class="ubbcode-body">The pic does give that effect.
    If it was angled up, I wouldnt have this problem.
    I may have an issue of getting down to a 100 yard zero...right? </div></div>

    No if the front is higher it would be giving you the exact problem you are having.

    It has to be a mount issue if that scope has tested okay on another rifle. That base looks real funky to me as wel. Being your receiver is higher on the front than the back, it looks like the back is not raised enough to make things square.

    What kind of base is it?
     
    Re: Question re: optic set-up

    I'll be it's one of two things.

    Incorrect base for that receiver.

    Front scope ring is taller than rear. (I think it looks like this one)

    Pull off the scope rings and hold them to one another, same height?
     
    Re: Question re: optic set-up

    rhutch,

    That's a Zeiss Diavari 3-12x56 T on board, right? According to Zeiss it has only 36.7" of adjustment. That's 18.35" up or down. Somehow you "lost or used up" all 18" of your up adjustment. How much windage adjustment (L or R) did you use to get sighted in 6" low @ 100 yds? Using a lot windage adjustment can limit your elevation adjustment.

    Either your rifle, base, rings, or scope is introducing 24 MOA of upward cant, rather than downward cant like that produced by a 20 MOA base. Normally when a bullet leaves the barrel it crosses your line of sight (LOS) twice: once on the way up and again on the way down (or rather right on your LOS when correctly sighted in to be dead on @ 100). In your case the bullet is never crossing your LOS. It starts out in your barrel, 1 1/2" to 2" below the LOS (and your scope), and finishes 6" below LOS. Think of it this way, your LOS is level, your barrel is pointing down...not up.

    If this were my rifle, I would begin by doing Trouble Shooting 101, by changing something. The easiest and cheapest way is to contact your custom base maker and explain your problem. Maybe the maker will agree to swap out your base for another, as I suspect the base maybe the culprit.

    Failing that you could spend $50 or so and buy a pair of Burris Signature Zee Rings. These will allow you to "get back" the 20 MOA you lost by allowing you a full 20 MOA of down cant. If it is the receiver rather than the base again your custom base maker can help. I notice you do not mention the makers name?

    Other than that I'm fresh out of ideas...

    Best of luck,

    Bob