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Thread: Barrel worn out?

  1. #1
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    Barrel worn out?

    I've put about 6500 rounds through my AR in the last three years. Barrel is LMT chrome-lined 14.5", 1/7 twist. It used to shoot 2-3MOA groups @100 yds with 55grn ammo, now rounds are scattering all over the place in about a 8" circle. After cleaning the gun I benched & rested it on sandbags yesterday, and with match grade 69grn ammo got sub-MOA groups. I tried the 55grn again and got flyers all over the place again.

    So, is the barrel done & dusted or is there anything that can be done to make it work with lighter bullets? I've still got about 1K rounds of 55grn that I'd prefer to shoot rather than sell to get expensive match grade ammo.

  2. #2
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    Quote Originally Posted by hkusp View Post
    I've put about 6500 rounds through my AR in the last three years. Barrel is LMT chrome-lined 14.5", 1/7 twist. It used to shoot 2-3MOA groups @100 yds with 55grn ammo, now rounds are scattering all over the place in about a 8" circle. After cleaning the gun I benched & rested it on sandbags yesterday, and with match grade 69grn ammo got sub-MOA groups. I tried the 55grn again and got flyers all over the place again.

    So, is the barrel done & dusted or is there anything that can be done to make it work with lighter bullets? I've still got about 1K rounds of 55grn that I'd prefer to shoot rather than sell to get expensive match grade ammo.
    It depends on a lot of things, to tell if its really smoked you need to have the head-space checked. That seams like a very large degradation in accuracy all at once and I think you should check your muzzle crown, if it became damaged during cleaning or whatever, its an easy fix to re do a crown. Also check out the entire weapon and your optic don't just assume its the barrel.
    "After I shot myself, my training took over and I called my parents..." Texas Grebner

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  3. #3
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    Since its still shooting good with good ammo I would have to think it could be a problem with the lighter cheap ammo. I could be wrong but I would think if its shot out or has a crown issue you would see it with the expensive ammo as well as the cheap stuff?

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    Nevermind.
    Last edited by Heavy Metal; 05-14-13 at 14:26.
    My brother saw Deliverance and bought a Bow. I saw Deliverance and bought an AR-15.

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    Its not a bench rifle to begin with, just shoot it the way it is suppose to be shot.

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    Quote Originally Posted by 2k12ss View Post
    Its not a bench rifle to begin with, just shoot it the way it is suppose to be shot.
    Yeah. But if it can't hold at least 4 moa with regular 55 grain, forget it.

    I can't see the barrel being worn out with that low of a round count... unless those 6500 rounds was only a handful of range trips..
    "You people have too much time on your hands." - scottryan

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    Faster twist barrels will wear out faster than a slower twist 1-9 barrels, and who knows how fast he was putting rounds down range. 1-7 barrels prefer heavier bullets anyway.

  8. #8
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    Quote Originally Posted by 2k12ss View Post
    Faster twist barrels will wear out faster than a slower twist 1-9 barrels, and who knows how fast he was putting rounds down range. 1-7 barrels prefer heavier bullets anyway.
    Not that much faster, only slightly faster.
    My brother saw Deliverance and bought a Bow. I saw Deliverance and bought an AR-15.

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    Sounds like your rifle has probably a normal amount of Throat Erosion( 6,500 rnd's) which would explain why the shorter,( 55gr projectiles ) are producing a larger spread, and the longer projectiles are still producing tighter groups... Less bullet jump to the Rifling of the barrel... At least in theory...
    You can probably continue too shoot the 55grainers, if you don't mind the accuracy, or step up to a longer projectile... 62-70grn and see how they perform...
    Last edited by Sierra276; 05-14-13 at 17:12.

  10. #10
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    My experience with worn out barrels is with 30-06 not 5.56 but here it is: Worn out barrels often, usually shoot stronger bullets better. In the case of 30-06 I have seen several rifles that would not shoot match ammunition worth a shit but would shoot the black tipped armor piercing bullets quite well. The AP bullets were longer and stronger than the usual 150 grain ball projectiles. The thinking was that a stronger bullet got gripped better by worn out rifling than a bullet of softer construction. You may be seeing a comparable situation.

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