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Thread: Diagnosing shift in PoI problem

  1. #11
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    Mar 2013
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    Kali
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    Are you adjusting your cheek weld during groups? If so, keep a solid cheek throughout each group and this will minimize parallax.

    Also check that your optics are 'loaded forward'. The Larue mounts usually dont allow for much wiggle room, but they should be pressed forward (toward the muzzle) as you clamp them down. The mount/scope is wanting to move forward under recoil. Same goes for the optic 'loaded forward' to the mount if it mounts with a cross-bar (ACOGS dont IIRC).

  2. #12
    Join Date
    Feb 2008
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    Update

    As most people speculated/assessed, it was probably an assembly problem.

    I tore down the carbine a few days ago, and immediately put it back together. I did the old "snug up three times" process, then set my wrench for 30 ft. lbs. and torqued. Not aligned for gas tube. Set the wrench to 40 ft. lbs., torqued, and it was aligned. Finished assembly.

    I also tightened the mount/scope connection. It wasn't exactly loose, but would tighten about 1/8 turn.

    Groups have shrunk by about 1/3rd (about 2" at 50 yards with a 1.5x ACOG and federal XM193). Groups with irons are the same (my usual). No wandering zero or shift in PoI.

    It just goes to show that I need some more experience assisting others to do a build.
    'That whole effort was held together by sweat, shame, and a tiny bit of pride.' -- Son of Commander Paisley

  3. #13
    Join Date
    Jan 2008
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    AZ-Waging jihad against crappy AR's.
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    Thanks for the update. As I have mentioned before if you don't want to be chasing torque all day, simply set it to 30 ft./lbs. and then leave it. If it doesn't align at that point then apply steady pressure until it lines up and stop. The chances of you going to 80 are pretty slim IME.

    Quote Originally Posted by Amicus View Post
    As most people speculated/assessed, it was probably an assembly problem.

    I tore down the carbine a few days ago, and immediately put it back together. I did the old "snug up three times" process, then set my wrench for 30 ft. lbs. and torqued. Not aligned for gas tube. Set the wrench to 40 ft. lbs., torqued, and it was aligned. Finished assembly.

    I also tightened the mount/scope connection. It wasn't exactly loose, but would tighten about 1/8 turn.

    Groups have shrunk by about 1/3rd (about 2" at 50 yards with a 1.5x ACOG and federal XM193). Groups with irons are the same (my usual). No wandering zero or shift in PoI.

    It just goes to show that I need some more experience assisting others to do a build.



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