barrel twist in AR style 223

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by catfire, Dec 29, 2010.

  1. catfire

    catfire Member

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    I know very little about the AR platform but want to build a very accurate AR....local smith tells me 1-7 twist and I think 1-8......I shot long range, Palma "F" class for awhile and with much sucess ....but know little about the AR.....M14 in service....
     

  2. SBruce

    SBruce Well-Known Member

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    Sierra says 1-7 or 1-8 for the 80 grn Matchking. They say 1-6.5 for the 90 grn Matchking.

    Berger says you'll need 1-7 or faster for the 90 grainers.

    Guess if you're gonna use it for really long range, 1-7 might be the way to go. You might get lucky and be able to shoot either bullet that way.

    I went with 1-8 in mine, but I have no intention of shooting anything heavier than 75-77's. Supposedly, the heavier bullets have to be loaded single shot, and what's the use of having a semi auto that's gotta be shot single shot.
     

  3. ICANHITHIMMAN

    ICANHITHIMMAN Well-Known Member

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    I have 1-7 its the best balance for shooting 55 to 77g bullets. Anything bigger than that your most likly going to have to single round load.

    What are you going to do with the rifle? Do you plant to shoot heavy bullets if so get the 1-7.

    The Military uses a 1-7, some SPR rifles where build with 1-8 at first but then switched to the 1-7 when they standaridized the MK262 OTM round (77gSMK).
     
  4. Kevin Thomas

    Kevin Thomas Well-Known Member

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    Catfire,

    The 1x8"s are pretty much standard fro everything up to and including the 80 grain Match bullets, but you didn't really specify what you're going to be doing with this. I'd only recommend the 80s and above for a competition gun, since they're all designed to be single loaded, and seated out well beyond mag length (2.260"). If you're not doing anything heavier than the 69s, then a 1x9" or even 1x10" will work just fine. As always, it's the heaviest (longest) bullet you'll ever want to use that will determine just how fast you need to twist the barrel.

    What are you planning on doing with this one? Answer that, and we'll be able to give you some clearer options here.
     
  5. catfire

    catfire Member

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    Wow ......real answers.....this gun will be used as defense gun only....maybe county sherriff work down the line....no targets longer than 300 most 80 and under...sniper competition very possible... accuracy is #1...mobility #2....looking at White Oak Armory SDM barrel but wonder about the 20". tks
     
  6. Mikecr

    Mikecr Well-Known Member

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    Ok, 300yds is not 'long range', so this gets way way easier than you're making it here.
    Just focus on serious accuracy within this application, as this trumps all else..

    Assuming you reload(wasted thread if not):
    You can go standard 12tw, or 14tw, and use flat base BR bullets ~52gr.
    And with this, you can load develop to achieve clean cold barrel accuracy

    I don't have an AR15 anymore, but if it were me for your use, I'd set it up with a ACOG type (both eyes) sight, Harris swivel bipod, best cut rifled barrel, and best trigger available. And I wouldn't deploy the gun until I could could kill a 2" dot at 200 -one shot, on demand.
    With components available today, I think this is a reasonable goal. But I don't think you'll get there using spears just between point first and blowing up.. These bullets just don't shine up close.
     
  7. ICANHITHIMMAN

    ICANHITHIMMAN Well-Known Member

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    Guys your twist rates and barrel choices are way off for what he just listed as user needs. No target longer than 300 and he wants mobility. Sherrriff work?

    You should look at an SPR barrel no longer than 18" from BCM, Noveski or Daniel Defence. That will afford you the greatest mobility and allow you to reach out to 800 yards. The gold standard 5.56 LE load in Hornady tap 55g.

    ACOG sights are great but only designed to be use with 62g bullets and each sight for a diffrent barrel length. The BDC for the 7.62 nato ACOG works great for the 77g MK262 OTM rounds.

    White oak makes good barrels but 20" is just to long for mobility.
     
  8. SBruce

    SBruce Well-Known Member

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    For whatever it's worth, I've had 3 different Ar-15's over the years. One had a 1-7, the last two have 1-8. I still have the last two. I think maybe I could be using 1-9 quite easily, because my most recent one seems to like the 60 grain bullets. It doesn't seem to like the 55 grain stuff I've tried. 69's and 77's shoot decent, but best accuracy has been with 60's so far........especially with factory ammo. The 1-7 was only gauranteed accurate with 69 and heavier bullets.

    I am thinking you'll want to use something in the 55-69 grain loadings (based on your 2nd post). I know that some Tactical ammo is available in 55 and 68-69 loadings from more than one manufacturer. A 1-8 or even 1-9 (as Kevin said) should theoretically shoot all those just fine. I've often wondered if I should have went with 1-9.

    Of the 3 I've had, the best for mobility was the shortest one (18" heavy barrel).
    I would consider 20" medium weight barrel to be max for quick mobility, especially if your talking about getting it into and out of a vehicle or the vehicle window fairly quickly.........These shorter barrels probably won't shoot the heavier bullets as efficiently as the lighter ones.

    Just my 2 cents.
     
  9. Loner

    Loner Well-Known Member

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    For LEO work you are still going to want to fire the glass penetrating rounds as well
    as the frangible ones. I would look into the cartridges first , then the gun. RRA seems
    to be following the market as well or better than anyone right now. What they are
    offering in an LE design is probably close to the mark. Not that I am advocating their
    product one way or the other.