Can Parallax Adjustment Greatly Affect Point of Impact at Various Ranges?

Discussion in 'General Discussion' started by FullCurlHunter, Oct 30, 2007.

  1. FullCurlHunter

    FullCurlHunter Well-Known Member

    Apr 5, 2006
    My Weatherby Mark V Ultra Lightweight chambered in 300 Weatherby was a tack driver and with the very same load as I regularly shot .5 inch groups with at 100 yards recently shot as follows.

    100 yards, great .5 inch group 3 inches high. I could cover the 6 shot group witha quarter.

    I cleaned the barrel and went down to 300 yards. I adjusted the side paralax from 100 to 300 to accomdate the yardage change. I en started hitting 7-8 inches high where I then had to re sight in to be dead on at 100.

    I went out again today adjusted paralax to 100 and from a clean barrel I was 3.5 inches high at 100 with sub par groups. I took it out to 300 adjsuted paralax to 300 yard setting and then shot 5 inches low at 300 where the previous day at the range I was dead on at 300 yards.

    Have you ever heard of adjusting the parallax and it greatly affecting the point of impact at various ranges? I think something is messed up with my scope and this is the only variable I can think of besides shooting with swivel bipods.

    What are your guys' thoughts on swivel bipods, my dad thinks it is the swivel bipods throwing everything off. I think it is something to do with my scope. It is a Zeis 4.5-14x44mm conquest never been biumped ever...

    Thanks for your thoughts

  2. HeskethPritchard

    HeskethPritchard Well-Known Member

    Nov 12, 2006

    If an optical instrument is imprecisely focused, the cross-hairs will appear to move with respect to the object focused on if one moves one's head horizontally in front of the eyepiece. This is why it is important, to carefully focus in order to 'eliminate the parallax', and to check by moving one's head.

    Not sure if this is helpful to you.

    I know on my scopes that have parallax adjustment they are not precise but I have not done enough testing at the longer ranges to determine how good or bad they are.

  3. devildoc

    devildoc Well-Known Member

    Feb 10, 2006
    I have the same scope on my .338win, and like Mr. Hasketh just said, don't trust what the dial says. Sit down at the bench and play with the paralax untill the crosshairs stay put when you wiggle your head around, then make a note of where the dial was when it was set right.
    The bipod could also be effecting POI if you are loading the bipod differently from group to group. Some rifles like a forward load some like a rear load and some like no load. Ya gotta get to know your setup and figure out what she likes. Was your cheek weld consistant from group to group? That could also be playing a factor.
  4. CatShooter

    CatShooter Well-Known Member

    May 8, 2001
    Well, to start off, because you made a change in the parallax setting, does not necessarily mean that is the reason for other changes, so don't automatically over look other posibilities.

    That being said.

    Mostly, the calibrations on the parallax of a scope do NOT directly correspond the actual ranges.

    This is something that you must test and verify. Then keep a cheat sheet for the adjustments on your regular tracking range notes.

    Also... you must always adjust the parallax from the same direction, because the tracking forks have play in them. I can't speak to the Zeiss, but Leupolds must be adjusted from the larger distance to the shorter distance ALWAYS!!

    That means if you want to go from 100 yds to 500 yds, you must go to the end (past infinity) then back to 500... if you want to go from 500 to 100, you can go directly from 500 to 100, but not the other way around.

    For a Zeiss, you should test it and determine which direction the play comes into effect.

  5. Brown Dog

    Brown Dog Writers Guild

    Sep 26, 2003
    I think you're telling us everything was fine until you started using a 'swivel bipod' .....if so,

    Your dad is right.

    [I'm quoting myself from an answer to a similar thread: ]

    Last edited: Oct 30, 2007
  6. AJ Peacock

    AJ Peacock Well-Known Member

    Oct 7, 2005

    How tall is your bipod? The taller the bipod the harder it is for me to stay consistent.