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Thread: 1/7 twist and 55 grain rounds

  1. #21
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    Quote Originally Posted by chp5 View Post
    The most accuarate barrel I have with 55's is an old A1 pencial barrel - 1/12. Incredible accuracy with the right loads.
    Indeed. There was an old military chart posted over on TOS a few years ago showing that with 55 gr ammo, 1/12 was the optimal twist for accuracy.
    "You people have too much time on your hands." - scottryan

  2. #22
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    Thumbs up

    I have fired several types (including Wolf) of 55 grain ammo thought a 1/7 barrel (Colt 6920) with an eotech sight and bipod. I regularly shot 1 1/2 inch groups at 100yards, but have found to maintain consistent groups, you must fine tune/re-zero your weapon, depending on the type of ammo being used. I got surprisingly good accuracy from Fed xm193, Wolf military classic, Wolf Black box, PMC Bronze, Winchester Q3131, and American Eagle. All 1 1/2 groups, but I did have to fine tune. YMMV.

  3. #23
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    Once a bullet is adequately stabilized, the riflings' rate of twist has no further influence on bullet accuracy.

    Light .224" bullets suck for accuracy at longer distances merely because they drift more in the wind.

    The dimensional consistency of your bore and chamber have a hell of a lot more to do with accuracy than twist rate ever will.

  4. #24
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    "We all have our idea of what is acceptable".
    In my opinion minute of angle is acceptable to 400 meters and most high quality 55 grain ammunition will do that in any decent AR15 1-7 twist rifle.

    4" groups at 400 meters is plenty acceptable to me and that is what I can wring out of my 1-7 rifles using 55 grain bullets.
    My Government profile and heavy barrel 1-9 twist rifles won't do much better, my Match guns will.

    62 grain M855 is even worse than 55 grain M193 in the accuracy department in my opinion.

  5. #25
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    I always notice that 1x12 does very well with 55gr.

    Noticeably more accurate than in 1x9 or 1x7 (for me). The difference in 55gr in 1x7 and 1x9 is hard for me to see unless I'm using really high powered scopes even then it's pretty nill.
    Chief Armorer for Elite Shooting Sports in Manassas VA
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  6. #26
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    Quote Originally Posted by chp5 View Post
    Is there any loss of accuracy if you shoot 55 grainers out of a 1/7 twist barrel?
    Quote Originally Posted by C4IGrant View Post
    Typically if I am getting half inch groups at 100yds, I will see groups open up by about .25 around the 110-130yd mark.


    C4
    There is only a "loss of accuracy" with that configuration (leaving out problems with the nut behind the trigger ) if

    A. your BBl just doesn't like the ammo(which can be a problem no matter what BBl twist bullet combo you try) or

    B. over rotation is a problem with the particlular bullet you are shooting. ie you might a shoot v-max bullet and have it fly apart due to over rotation but a Barnes bullet of the same weight may hold up better and shoot fine. Its a funny thing how one 1-7 twist BBL might shoot 55 grns just fine and the next won't shoot them worth a darn, but it is true. When you get on the edge of the Bullet weights (high or low) your twist rate was designed for, you just need to shoot N See...there is no other way to know. It's a far better practice to simply stay in the middle of the road so to speak with BBL Twist and Bullet weight. ie a 1-12 twist with those 50-55gr etc.



    "Typically if I am getting half inch groups at 100yds, I will see groups open up by about .25 around the 110-130yd mark."????

    Pardon me, but that doesn't compute in my mind.

    I believe the only way you get a 50% increase in group size within 10-30 yds is lucky/ misleading groups at 100 yds or poor shooting at 110 yds. That is not an ammo problem. If the bullet survived the first 100 yds in tact, the centrifigal forces acting upon it have decreased greatly and have less negative effect not more at longer ranges.???

    Thats just me tho. Shrug?

  7. #27
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    The only main time you should get issues in a few yards/meters is when the bullet is going from sonic to transonic fligth -as its not affected buy its own wind forces.

    I've shot 55gr out of 1:7's (only twist I own) out to 500m with decent results (it does seem to get a lot worse between 300 and 500 though)
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  8. #28
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    Quote Originally Posted by ricky_arthur View Post
    There is only a "loss of accuracy" with that configuration (leaving out problems with the nut behind the trigger ) if

    A. your BBl just doesn't like the ammo(which can be a problem no matter what BBl twist bullet combo you try) or

    B. over rotation is a problem with the particlular bullet you are shooting. ie you might a shoot v-max bullet and have it fly apart due to over rotation but a Barnes bullet of the same weight may hold up better and shoot fine. Its a funny thing how one 1-7 twist BBL might shoot 55 grns just fine and the next won't shoot them worth a darn, but it is true. When you get on the edge of the Bullet weights (high or low) your twist rate was designed for, you just need to shoot N See...there is no other way to know. It's a far better practice to simply stay in the middle of the road so to speak with BBL Twist and Bullet weight. ie a 1-12 twist with those 50-55gr etc.



    "Typically if I am getting half inch groups at 100yds, I will see groups open up by about .25 around the 110-130yd mark."????

    Pardon me, but that doesn't compute in my mind.

    I believe the only way you get a 50% increase in group size within 10-30 yds is lucky/ misleading groups at 100 yds or poor shooting at 110 yds. That is not an ammo problem. If the bullet survived the first 100 yds in tact, the centrifigal forces acting upon it have decreased greatly and have less negative effect not more at longer ranges.???

    Thats just me tho. Shrug?
    It could have been the batch of ammo I was using. Will try and and get some different ammo to test.

    I have the same experience going the other way (1/9 twist with 77gr ammo). After about 110yds, I notice that my groups open up.



    C4

  9. #29
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    Off topic I guess but...

    I have a 1 in 9 twist 16 inch barrel...Whats the heaviest bullet that commonly works well with that twist?

    I'm looking for the heaviest, ACCURATE round...I intend to deer hunt with my AR (its legal here, and I'm a good shot)...I was thinking 68 - 70 grains...specifically the Barnes Triple Shock (62 or 70 gr.) or possibly the Federal factory load using the 60 grain Nosler Partition bullet. Than You.

  10. #30
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    your 1-9 twist should shoot any of the bullets you listed just fine.


    Ricky

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