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Thread: Quick Noob Question About Barrel Twist Rate

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    Quick Noob Question About Barrel Twist Rate

    So, if I get real lucky, I may be aquiring a new rifle sometime in the near future. All the rifles I am looking at have 1:7 twist barrels.
    I found a couple helpful threads, (https://www.m4carbine.net/showthread.php?t=54287&page=6 {Which Twist Rate}) (https://www.m4carbine.net/showthread.php?t=19881 {5.56 mm Duty Loads}) and it's clear to me that the 1:7 barrels are good.
    But one thing not answered very well for me, was the way the 1:7 barrels will affect lighter ammo- I see a lot of people saying that it's great with heavier bullets, and a few saying it works all around, but for me it's not very clear- so here's my main question:
    What I'm currently, and intending, to shoot is the basic 55 gr. FMJ stuff. I don't intend to use anything lighter, but at some point possibly heavier (or at least, the option to use a heavier round will be there).

    Will the 55 gr. bullets work just as well in a 1:7 barrel as heavier bullets? (i.e., no loss of accuracy/reliability/velocity, etc.)
    Last edited by Jellybean; 06-29-10 at 18:09.
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    Quote Originally Posted by Jellybean View Post
    Will the 55 gr. bullets work just as well in a 1:7 barrel as heavier bullets? (i.e., no loss of accuracy/reliability/velocity, etc.)
    Check these out: https://www.m4carbine.net/showthread...ght=twist+rate

    https://www.m4carbine.net/archive/in...p/t-20501.html

    My search: http://www.google.com/#hl=en&q=site%...2625539515e101

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    In my humble opinion I'd rather have a 1-7 and shoot lighter bullets out of it, than have a 1-9 or 1-12 and try to shoot the heavies out of it.

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    Thanks!
    Read the top two, and all the 1st page google results.
    So using my amazing powers of deduction...
    I guess I'd be pretty safe in saying that 55gr. will work just fine in a 16" 1:7 barrel....
    "Once we get some iron in our souls, we'll get some iron in our hands..."

    "...A rapid, aggressive response will let you get away with some pretty audacious things if you are willing to be mean, fast, and naked."-Failure2Stop

    "The Right can meme; the Left can organize. I guess now we know which one is important." - Random internet comment

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    Quote Originally Posted by Jellybean View Post
    Thanks!
    Read the top two, and all the 1st page google results.
    So using my amazing powers of deduction...
    I guess I'd be pretty safe in saying that 55gr. will work just fine in a 16" 1:7 barrel....
    Good news. For future reference utilize the format in my Google search, my sig line, and you'll usually find what you're looking for. I do believe we'll be getting a Google search engine feature in the near future here on M4C and that will help a lot. Best of luck.

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    In theory, the extra energy needed to drive a bullet through a tighter twist could cause a drop in velocity.

    A faster twist can have two affects on the lighter bullet. 1) It spins the bullet too fast causing a less stable flight resulting in less accuracy. 2) A combination of tight twist, fast velocity and light bullet construction can cause the bullet to fail in flight from centrifugal forces. In a very extreme case, the bullet will "skid" down the barrel instead of being engraved by the rifling.

    This isn't to say a 1/7 twist barrel will not shoot 55gr bullets. Some will shoot them accurately and some won't. Some barrels will shoot some 55 gr bullets better than others. You just have to try them in your weapon and see, just like any other firearm

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    Quote Originally Posted by Jellybean View Post
    Will the 55 gr. bullets work just as well in a 1:7 barrel as heavier bullets? (i.e., no loss of accuracy/reliability/velocity, etc.)
    For all practical purposes, yes.
    You can go down the rabbit hole of minutia and extreme examples, but for distances at which 55gr rounds are applicable there will be no real repurcussions.
    Also keep in mind that each barrel is a little different and will prefer certain bullets at certain velocities, but once again, you have to decide how minute a difference is applicable to your employment.
    Jack Leuba
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    1:7 is considered best all around now if your gonna shoot only light loads from a weekend warrior why not get the 1:9

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    Quote Originally Posted by petergun870 View Post
    1:7 is considered best all around now if your gonna shoot only light loads from a weekend warrior why not get the 1:9
    I think a better question is why get a 1/9. A 1/7 will do anything a 1/9 will do and more.

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    Quote Originally Posted by petergun870 View Post
    1:7 is considered best all around now if your gonna shoot only light loads from a weekend warrior why not get the 1:9
    Quote Originally Posted by MistWolf View Post
    .....This isn't to say a 1/7 twist barrel will not shoot 55gr bullets. Some will shoot them accurately and some won't. Some barrels will shoot some 55 gr bullets better than others. You just have to try them in your weapon and see, just like any other firearm
    Well, I guess I should have explained this a little better to start with.
    My current rifle actually does have a 1:9 barrel, but I'm in the process of working on upgrading. My current top picks (DD and BCM) both have the 1:7 barrels. I just wanted to be sure about this issue before dropping 12-13 hundred bucks on one, and then finding out I screwed myself because I now have a ton of ammo sitting around that's so completely unreliable/inaccurate, that it's unusable. Or be forced to get more expensive ammo to use just drilling.
    "Once we get some iron in our souls, we'll get some iron in our hands..."

    "...A rapid, aggressive response will let you get away with some pretty audacious things if you are willing to be mean, fast, and naked."-Failure2Stop

    "The Right can meme; the Left can organize. I guess now we know which one is important." - Random internet comment

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