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.223/5.56 grain question?

Discussion in '.223 Remington/5.56 NATO' started by stigmata, May 12, 2013.

  1. stigmata

    stigmata 20g

    Messages:
    972
    My M&P is a 1 in 8 twist barrel, and have only used 55grain rounds.
    Now I have seen 62grain and higher, and was curious what is the highest grain I can use with a 1 in 8.
    Or better yet what grain should I stay between for the gun to fire properly.

    I've heard if you go too low it will not cycle properly and too high you risk damage to the barrel from the hotter round. Havent seen anything in black and white to tell me the difference and limits to use, just info I have got from ppl when I came across different grains of .223/5.56 ammo.

    Any info would be a great help....
  2. LAZY EYED SNIPER

    LAZY EYED SNIPER Overwatch Staff Member Global Moderator Supporter "Philanthropist"

    Messages:
    21,108
    A 1:8 twist will be able to handle most any bullet weight you can find.

    Might not stabilize the heavier 75gr and above as well as a 1:7, but I certainly wouldn't worry about causing any damage. I'd suggest picking up a few different weights to see what yours likes. My 18" SPR barrel is a 1:8 and really likes the 62gr xm855 ammo...
  3. oli700

    oli700 12g Supporter "Philanthropist"

    Messages:
    9,269
    You are confusing projectile grains with powder grains.....if you were asking about powder charge you would be correct.....your asking about projectile weight measured in grains. The tighter the twist the heavier bullet it will stabilize to a point, you don’t want too tight of a twist or it will cause too much drag.

    1 twist in 8 inches of barrel is said to be the best all around choice for AR 15 ammo.
  4. John A.

    John A. I'm "THAT" guy Staff Member Global Moderator Moderator

    Messages:
    14,674
    It is.

    For the simple reason that a 1:7 twist does not stablize very light bullets and 1:9 doesn't tend to stablize the heaviest bullets. The 1:8 is about the best twist you can get for the widest range of bullets.

    And as LES pointed out, shooting 75 gr bullets won't hurt any barrel. Just that some barrels with certain twists won't stablize the bullets as well as others and won't be as accurate at longer ranges. But you can shoot them all day long if you want to. I even specifically keep a mag loaded up with 75gr hornady's to use in my sbr just because I can and don't worry about long range accuracy because that was never intended for that upper. It's reserved for local calls and that's the heaviest pill I have for it.

    But truthfully, for short barrels, I do prefer a 1:7 twist just due to the shorter contact area of the rifling to impart as much spin on any bullet that goes through it in the shortest amount of time just so it will give it a leg up on accuracy at longer distance with any bullet I use, though short barrels were never intended for extended range engagements anyway.

    Just my humble 2 cents.
  5. stigmata

    stigmata 20g

    Messages:
    972
    Thanks for the info guys, I really appreciate the input.
    I am talking about projectile grain and was just wanting clarification as to what I I'll told about different grains from the shop I buy ammo from, as not all ppl working there really know all the answers to questions.
    I am not too worried about long range accuracy, since I'm not out to snipe ppl, just to shoot at the range and no more than 50-75 yards out.
    I'll be sticking with 55 or 62 grain, and may just try a box of 75 to see what it does. Thx again guys.

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