First round High, then groups fine
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Thread: First round High, then groups fine

  1. #1
    Carbineman werewolf's Avatar
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    First round High, then groups fine

    I've been getting some accuracy issues from my 6.8 barrel / bolt. First round goes high and then the next rounds are around 1.5 moa. This doesn't happen with my 5.56 barrel / bolt. Any suggestions?

  2. #2
    Rifleman Whole Bunches's Avatar
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    Re: First round High, then groups fine

    I assume you mean the first round fired from a freshly loaded magazine which has been inserted into the XCR and not the very first round of the day fired from a cleaned barrel. I had the same thing happening in one of my AR uppers in .223. I tried differing approaches: letting the bolt go forward with the bolt release; letting the bolt go forward by pulling back the charging handle and then letting go; not letting the gun run dry by leaving a round in the chamber and inserting another loaded magazine. In the first 2 choices it wasn't chambering the round with the same force as having fired the rifle so the bolt wasn't locking up exactly the same. The more I fired it, the less the first round would be off; finally the first round stayed in the rest of the group. I figured the bolt lugs finally wore in with the barrel extension and made the whole area smooth enough that the bolt always locked up the same, regardless of force.

    Advice: keep on shooting and see if the situation improves.

  3. #3
    Carbineman werewolf's Avatar
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    Re: First round High, then groups fine

    That would make sense and yes, fresh mag, not cold bore, the 6.8 set up probably only has a few hundred rounds through it, unlike the 5.56 ;D which has been consistant.

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    Banned EricCartmann's Avatar
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    Re: First round High, then groups fine

    Quote Originally Posted by Whole Bunches View Post
    I assume you mean the first round fired from a freshly loaded magazine which has been inserted into the XCR and not the very first round of the day fired from a cleaned barrel. I had the same thing happening in one of my AR uppers in .223. I tried differing approaches: letting the bolt go forward with the bolt release; letting the bolt go forward by pulling back the charging handle and then letting go; not letting the gun run dry by leaving a round in the chamber and inserting another loaded magazine. In the first 2 choices it wasn't chambering the round with the same force as having fired the rifle so the bolt wasn't locking up exactly the same. The more I fired it, the less the first round would be off; finally the first round stayed in the rest of the group. I figured the bolt lugs finally wore in with the barrel extension and made the whole area smooth enough that the bolt always locked up the same, regardless of force.

    Advice: keep on shooting and see if the situation improves.
    If the round goes down range, did that not mean the bolt properly lock up?

  6. #5
    Carbineman werewolf's Avatar
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    Re: First round High, then groups fine

    Yup, and the more I think about it, it doesn't make any sense, but the mag tension and bolt scavanging off the top of the mag might have been what he was talking about. I don't know enough about that to make a judgement. All I do know, is this is happening and although the accuracy is close I'd like a "bit' more consistancy.

  7. #6
    Banned EricCartmann's Avatar
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    Re: First round High, then groups fine

    Quote Originally Posted by werewolf View Post
    Yup, and the more I think about it, it doesn't make any sense, but the mag tension and bolt scavanging off the top of the mag might have been what he was talking about. I don't know enough about that to make a judgement. All I do know, is this is happening and although the accuracy is close I'd like a "bit' more consistancy.
    Is this for 100 yards? If it is at 100 yards, then the higher one means it's going faster and due to more pressure. A round going faster the first shot, I have never heard of. Normally rounds go higher (string) the more the barrel heats up.

  8. #7
    Carbineman werewolf's Avatar
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    Re: First round High, then groups fine

    yes, at 100 yds. I'm not anticipating, I'm not recoil shy by any means, just don't get it.

  9. #8
    Marksman Camp Cook's Avatar
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    Re: First round High, then groups fine

    My experience is slower bullets due to being in the barrel longer hit higher than faster bullets...

  10. #9
    XCR Guru gunner69's Avatar
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    Re: First round High, then groups fine

    Try swabbing out your barrel out before shooting, just in case its the lube doing it. :2cents:
    Fio para bellator - be the Prepared Warrior

  11. #10
    Banned EricCartmann's Avatar
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    Re: First round High, then groups fine

    Quote Originally Posted by gunner69 View Post
    Try swabbing out your barrel out before shooting, just in case its the lube doing it. :2cents:
    Don't think that's it, he said it's the first round every mag.

    I can't see how a mag would cause this issue, the mag feeds or it does not feed. I can't see how it would alter the shot. I am going to say it's just coincidence. If it's not then just ignore the first round, and use the other 29 to zero.

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