Odd AR15 accuracy changes.

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  • Ljungman

    Marksman
    Rating - 100%
    3   0   0
    Nov 11, 2011
    230
    18
    Lake Superior
    Ok - i seem to be able to fix everyone elses issues but my own.
    I have been shooting a factory Anderson AM15. with my handloads its mostly a 1.5 moa rifle - standard anderson carbine 16" barrel, and consistently groups at that. its 1.5 all day...every day...with everything.
    This weekend i took it down, changed gas block, and took off the standard delta ring and hand guards. I placed a barrel nut with free float handguard and new aero micro gas block on. put on new barrel nut and got it tight (supplied wrench and nut design did not leave me ability to get torque wrench on it - its greater than 40 foot pounds i can guarantee.)
    Now that gun is free floated.....its cycling like a champ, ejection is strong and consistent. Accuracy has gone to complete hell. its a 6 inch gun at 100 yards using same ammo. Gun shot several rounds at 4 inch at center/poa, and then poi shifted up and to the right becoming highly erratic.
    Im suspecting scope the mounts are tight, and rings are tight. unknown if it failed internally- but wanna make sure im not missing anything mechanical in the process. gas block seems to be sealed tight, carrier and tube arent rubbing, bolt is smooth when operated by hand - no resistance. i can see no play with upper in block and me yanking on barrel, and can see nothing touching barrel after the nut.
    and scope - loyal as it has been...is a suspect. plan on borrowing an optic to check with this week.
    im open to ideas, theories and suggestions.
     

    Vigilant

    Grandmaster
    Rating - 100%
    21   0   0
    Jul 12, 2008
    11,659
    83
    Plainfield
    The above posted by Rookie is correct, didn’t look at the other post, but if you had an inch and a half Anderson, I personally wouldn’t have ****ed with it. As that is better than ANYTHING Anderson I’ve ever seen, and that’s havinf fixed a plethora of “my Anderson won’t work” rifle/carbines.
     

    Ljungman

    Marksman
    Rating - 100%
    3   0   0
    Nov 11, 2011
    230
    18
    Lake Superior
    Yeah regretting it now. Got a free float rail and nut new in trade. Thought I could get that down to moa. Now it's 6 moa...and eratic. Got a loaner scope I'm going to try this week to rule that out.
     

    leftyM4

    Plinker
    Rating - 0%
    0   0   0
    Oct 9, 2019
    55
    8
    Oregon City
    That is indeed a strange problem. Thing is if it was a problem with the rifle it would be consistant or gradually get worse or better. have to tried other ammo.

    You mentioned floating the barrel. is it vented? Some barrels get funny as they heat up especially cheaper barrels. If your old handguards were vented then it could be running hot. How many rds thorough the barrel? Once you get into the thousands the accuracy will dwendle. Did you check the crown for any nicks. It may be time for a deep cleaning the barrel to get rid of copper and lead fouling.

    Also one of your cross hairs could be loose so its still zeroed but every once in a while the recoil kicks it off target and the next shot puts it back on.

    Gas leaks could be the other cause. Nothing beats tapered pinned front sights the sets screw or clamp on type can wonder or wiggle. I can't even count how many times someone has had a problem with set screw or clamp on gas blocks. Also was it really tight like so tight that you might have to take a hammer to take off or did it slide on nice and easy. did you remember to put the gas tube retainer pin back in?

    Did you properly Torque the float tube? You can't just hand tighten them they have to be tightned to spec.
     
    Last edited:

    Tombs

    Grandmaster
    Rating - 0%
    0   0   0
    Jan 13, 2011
    12,021
    113
    Martinsville
    Try taking off your muzzle device and see if your accuracy improves. It's a long shot but if you're 100% sure you did everything else right, it's not out of the question that it could be an issue.

    I've experienced dramatic POI changes from different muzzle devices, as well as varying accuracy.
     

    praff

    Sharpshooter
    Rating - 100%
    29   0   0
    Sep 26, 2009
    585
    18
    New, proprietary barrel nut i assume??? Makes me wonder if somehow its not putting even pressure on barrel. Like its not cut square to the threads maybe. Or maybe it is bottoming somewhere before it tightens on the barrel shoulder. I would definitely inspect that interaction.
     
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