.223 Ammo Grains

Discussion in 'General Rifle Discussion' started by ExpressMagnum, Sep 15, 2013.

  1. ExpressMagnum

    ExpressMagnum New Member

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    I have a STAg AR15 with a 1/8 twist and TC Venture with a 1/12 twist. All of them are in .223 but I needed help to know what is the best grain if ammo I should be shooting ? I need your help these are new rifles never shot before and I don't want to destroy them... Thanks
     
  2. Overkill0084

    Overkill0084 Active Member

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    One for both? I'd guess that 55 gr ammo would be your best starting point. The Stag will shoot the heavier stuff better. The TC will likely not care for bullets much heavier than 55 gr.
    As far as destruction related problems, nothing much to worry about, just don't use 5.56 ammo in anything exclusively built for .223 only. Beyond that, if you pick a bullet weight your rifle doesn't like, you'll simply get degraded accuracy.

    This covers the bullet weight thing in detail: http://www.firearmstalk.com/forums/f20/understanding-barrel-twist-bullet-weights-44557/
     

  3. Tjurgensen

    Tjurgensen New Member

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    Like overkill said the 1-12 twist will be effective with 55 gr and below and the 1-8 will handle 60 gr and above
     
  4. DeltaF

    DeltaF New Member

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    Just don't go below 55 grains in the 1-8 and stay away from any milspec or .556 ammo and you'll be fine.
     
  5. samnev

    samnev New Member

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    For the 1:8 twist Stag, 69 grain Federal Gold Metal Match.
    For the 1:12 twist TC, Any Premium Ammunition in the 55-60 grain range.
    If you hand load I have had great success with 52 grain Sierra Match Kings with 26.2 grains of W748 in both the 1:8 and 1:12 AR's I own.
     
  6. icallshotgun88

    icallshotgun88 New Member

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    I had a bravo company 1:7 twist and I've been shooting mostly 55 grain because its what's available to me..

    I should be shooting 62-75 grain correct?

    And if I stick with the 55 grain what will the downsides be?
    Decreased accuracy? Too high? Too low? All over the place? It's pretty dead on up to 100 yards to far.
    ...guessing it won't make too much of a difference until >100 upwards?
     
    Last edited: Sep 16, 2013
  7. JimRau

    JimRau Well-Known Member Supporter

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    The Stag should have a 5.56 chamber.
     
  8. DeltaF

    DeltaF New Member

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    Below 55 in a 1:7 and you'll overspin the bullet. Accuracy decreases and fire the wrong ammo and it can come apart. 1:7 can handle just about as large of a grain .556 bullet as you can find. 55 should work just fine for you out to 150 yards or so. I wouldn't try anything smaller though.
     
  9. samnev

    samnev New Member

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    223/556 Ammo

    While I generally agrre with the statement you should not go lower than a 55 grain projo. The 52 grain SMK is a lot longer projo than the 55 grain projo and it doesn't get over spun in any of my 1:7 AR's and accuracy has been excellent in all my AR's from 1:7 twist thru 1:12 twist.
     
  10. Sniper03

    Sniper03 Supporting Member Supporter

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    The 1:12 twist will not effectively stabilize rounds above 62 grains. The 1:8 55-69 very well. But I would recommend staying with the 55 grain bullet since you have two different twist rates. I have a Rock River A-4 Varmint in 1:8 twist and on a good day with P223E Federal Ammunition in 55 gr. will group 1/4 inch groups on occasion. Doesn't get any better than that. So you can very effectively use the 55 gr. round in both. But a 69 grain round will keyhole on the target shot from a 1:12 twist.

    Velocity X *12=__________ Divided by the Twist Rate (12) (9) (8) or (7) =____________X *60 = RPM of the bullet leaving the bore! Equals RPM. (Choose Your Twist)
    We know most all 223/5.56 Ammunition velocity is more than 3000 FPS but we will use that velocity in the below examples.
    This gives you an idea of the Revolutions Per Minute it takes to stabilize a in flight.
    For example if the velocity was 3000 FPS the 1:12 Twist would equal 180,000 RPM while the 1:8 would equal 270,000 RPM. Using the formula above. A general rule is the heavier the grain bullet the faster the twist rate must be to stabilize the round in flight. The numbers with an * above are consonants in the formula always representing *Inches (12) and *Minutes (60).
    This does not mean that a 55 will not shoot good in a 1:7 but only that peak accuracy will normally be with heavier grain bullets.
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    Last edited: Sep 17, 2013
  11. DeltaF

    DeltaF New Member

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    There's an exception to every rule. SMK is some good stuff. The issues below 55 grain revolve around cheaper thin jacketed rounds coming apart. Sierra Match King is the opposite of cheap thin jacketed rounds. :D The overspin accuracy problems came into play at long distances though. Any .223/.556 that doesn't fly apart can usually shoot accurate up to about 100 yards.