Bullet weight and rifle twist

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    Grandmaster
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    Sep 22, 2008
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    Kokomo
    Help me out here...

    I'm shooting 55 grain 223 out of a 10.5 inch barrel that is 1:7 twist. Shooting from a lead sled and the bullets are all over the target - about a 3 inch group. I'm thinking it's more the twist rate than the barrel length. I've got a 16 inch barrel with 1:9 twist that I'm going to try tomorrow...

    Am I right or wrong?
     

    DoggyDaddy

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    Aug 18, 2011
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    I think generally speaking the lighter bullets (55 grain) do better with the 1:9 twist, whereas the 1:7 twist is better for 62 grain on up.
     

    KJQ6945

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    Help me out here...

    I'm shooting 55 grain 223 out of a 10.5 inch barrel that is 1:7 twist. Shooting from a lead sled and the bullets are all over the target - about a 3 inch group. I'm thinking it's more the twist rate than the barrel length. I've got a 16 inch barrel with 1:9 twist that I'm going to try tomorrow...

    Am I right or wrong?

    If you want good groups, shoot good ammo.
    I zeroed in the scope yesterday on my MK12 using XM193. Once zeroed, I put 5 rounds down range, and they weren't impressive at all. Read that, as all over the place.
    I then switched to Black Hills 77gr TMK. (Tipped MatchKing) 5 rounds I could cover with a dime.
     

    KJQ6945

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    Hornady V max...
    I'm pretty ignorant in twist rates and bullet weights. The MK12 has an 18" Douglas barrel, 1:8 twist. Black hills made the MK262 mod 1 ammo specifically for the gun. I just used the 55gr stuff to dial the scope in, since it's a whole lot cheaper. I was amazed at the difference in the groups though.
     

    55fairlane

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    Jan 15, 2016
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    What brand name is your barrel? Mill spec? If true mill spec 3 inch group at 100 yards IS acceptable by US military standards....so while yes good ammo in,better groups out,there are a lot of other factors that can affect accuracy

    Another good example of this is my 1022 shoots the same groups with Eley tennex or cheap bulk Federal, but Eley tennex way out shoots federal bulk in my Anschutz

    Aaron
     

    Woobie

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    Dec 19, 2014
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    It is not uncommon for lighter bullets in fast twist barrels to be less accurate. I'm not sure why, maybe too many RPM for a shorter bullet, possibly causing some yaw. That's just a guess, but generally lighter should have slower twist, heavy should be faster.

    Try some 62 or 69 grainers and see how they do.
     

    KJQ6945

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    I'm not sure, it was on a Seekins upper. I'm using this gun for coyote so I don't want minute of man.

    I would still recommend trying heavier ammo. You've got to find what ammo the gun likes, but it will most likely be a heavier bullet from what little I've read about it.

    text me if you've still got my info
     

    Trigger Time

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    Aug 26, 2011
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    1/7 twist wasn't designed to do great with 55gr ammo. With some 55gr it will do good. Obviously not yours and not most.
    use 62 grain and up. The heavier you get the better.

    1/9 twist was designed to stabilize and do well with 55 up to like 72 and maybe 79 I think.
    i haven't shot past that I don't think out of a 1:9. Memory isn't good lol
     

    KJQ6945

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    I'm not as up on .223 as I am .308 but, all bullets are restricted by caliber. So heavier really means longer. You run into problems getting them in the mag.

    The 77gr actually looks smaller than the 55gr. It has a polymer tip, and appears to have a more gradual taper than 55. No apparent difference in height. Must be a lot of extra weight on the back end. :dunno:
     

    Woobie

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    The 77gr actually looks smaller than the 55gr. It has a polymer tip, and appears to have a more gradual taper than 55. No apparent difference in height. Must be a lot of extra weight on the back end. :dunno:

    The 55 has a tangent ogive, which is the part that curves from the full diameter down to the tip. The 77 has more of a secant ogive, which is more of a straight line than a curve. So when loaded they will look smaller, even though you can see the real difference from that picture.
     

    ChristianPatriot

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    Feb 11, 2013
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    The 55 has a tangent ogive, which is the part that curves from the full diameter down to the tip. The 77 has more of a secant ogive, which is more of a straight line than a curve. So when loaded they will look smaller, even though you can see the real difference from that picture.

    The "hybrid" bullets are both. Secant up by the meplat for better ballistics and tangent up at the caliber so it's less sensitive to seating depth.
     

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