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Thread: Why would my 6920 shoot low?

  1. #1
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    Why would my 6920 shoot low?

    I was zeroing a couple of unfired ARs yesterday. At 15y, for a 'make sure I'm on paper' sanity check, I'm about 6 inches low. OK, maybe it's the blem PA dot? Nope, the irons are 6 inches low also.

    This is a 6920? the one that came without furniture? Fixed front sight, I put a full set of Magpul MOE and a MBUS rear sight on it, otherwise untouched.

    In the same session, my M&P barely needed adjustment, so I don't think it's me.

    Any thoughts?
    'Nobody ever called the fire department because they did something intelligent'

  2. #2
    What load are you using?


    Okie John
    “The reliability of the 30-06 on most of the world’s non-dangerous game is so well established as to be beyond intelligent dispute.” Finn Aagaard
    "Don't fuck with it" seems to prevent the vast majority of reported issues." BehindBlueI's

  3. #3
    Site Supporter JohnO's Avatar
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    Hard to say with minimal info.

    I would print the gun at progressively increasing distances to ascertain the actual sights vs. bore axis relationship. Perhaps a laser bore sighter is called for to determine the relationship. From what you described it sounds like your 6920 is launching rounds with a downward trajectory.

  4. #4
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    It's shooting 90s-era Georgia arms commercial reloads and 55 grain gold dot to the same point.
    'Nobody ever called the fire department because they did something intelligent'

  5. #5
    Site Supporter Lon's Avatar
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    Just to be clear, this 6920 has never been fired or sighted in? If it has never been fired or sighted in Previously, were you able to zero both irons and dot after these initial shots? If it has a front sight tower what does the front sight look like? Is the sight itself barely threaded in or is it seated pretty far down?
    Formerly known as xpd54.
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  6. #6
    Supporting Business NH Shooter's Avatar
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    Quote Originally Posted by Lon View Post
    If it has a front sight tower what does the front sight look like? Is the sight itself barely threaded in or is it seated pretty far down?
    My thought too, the front post needs to be lowered.

  7. #7
    THE THIRST MUTILATOR Nephrology's Avatar
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    With a 100M zero my irons and dots are about 3-4" low at 15Y.

  8. #8
    Quote Originally Posted by TQP View Post
    I was zeroing a couple of unfired ARs yesterday. At 15y, for a 'make sure I'm on paper' sanity check, I'm about 6 inches low. OK, maybe it's the blem PA dot? Nope, the irons are 6 inches low also.

    In the same session, my M&P barely needed adjustment, so I don't think it's me.

    Any thoughts?
    Un-fired rifles would be key for me. A question, though, if it's unfired how did you know the PA dot was on?

    Check your front sight and make sure that the base of the front sight is flush with the hole it goes into - that should mechanically zero the front sight. Center the windage on the BUIS and then begin the zeroing process. As long as the rifle groups and you don't run the front sight to the bottom or out the top of the FSB, and the windage isn't cranked too far left or right, you should be good to go.

    Then put on the red dot, adjust it so the dot is either sitting on (co-witness) or slightly above (lower 1/3) the front sight post through the iron sights. Then fold down the rear sight and zero the red dot.

    That's the way I do it on my fixed FSB rifles.

  9. #9
    Quote Originally Posted by Nephrology View Post
    With a 100M zero my irons and dots are about 3-4" low at 15Y.
    With a lower 1/3 co-witness your red dot should be about 2.8 inches above the bore, so about 3 inches low at 15yards is not too far off the path - certainly within my wobble zone.

    I was thinking he ought to be about 1.5 -2 inches low anyways at 15yards with a 25 yard zero, so really he was 4 to 4.5 low.

  10. #10
    Quote Originally Posted by JohnO View Post
    Hard to say with minimal info.

    I would print the gun at progressively increasing distances to ascertain the actual sights vs. bore axis relationship.
    Very much this. Distance reveals the true nature of our problem(s).


    Okie John
    “The reliability of the 30-06 on most of the world’s non-dangerous game is so well established as to be beyond intelligent dispute.” Finn Aagaard
    "Don't fuck with it" seems to prevent the vast majority of reported issues." BehindBlueI's

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