AR 15 experts.. 1 in 7 vs 1 in 9 twist?

Discussion in 'Rifle & Shotgun Discussion' started by Blitzkrieg, Mar 18, 2011.

  1. Blitzkrieg

    Blitzkrieg Well-Known Member

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    Everything I have now is 1/9 or 1/10 and they do well accuracy wise.. we use M855 and 62 to 70 grain HPs and these twists do great

    But I am trying to build my gal a new M4 type carbine and the only barrel that I want and that I can find is out of stock in the 1/9, but in stock in 1/7 twist

    What to do? I hear the 1/7 burn out faster, is that a realistic issue? Experiences?
  2. supergenius

    supergenius Active Member

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    I wondered too as I went 1:8
  3. jdub75

    jdub75 Well-Known Member

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    1/7 will stabilize a heavier bullet 72+gr. 1/9 does fine up to 64gr, some say up to 69gr. 1/8 is about perfect, but hard to find all the options in that twist. I've had 2 1/7 twist AR's, and they will NOT shoot lighter stuff well at all. I shot some 45gr HP's and they were all over the place at 100 yds on a high end barrel w/ scope. Switched to 69gr TAP, and was shooting groups about 1" at 100 yds with the same rifle. I'm working on a build now, and went with 1/7 so I can shoot heavier stuff for hunting. Also doing a precision build, and its a 1/8.
    If you/she is just gonna be plinking 55gr stuff, the 1/7 is fine. Prolly not gonna burn out the barrel unless she's shooting full auto or thousands of rounds a year. Besides, any barrel is a wear item.
  4. Shooter98

    Shooter98 Member

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    I agree. If you're going to handload then barrel twist may be a concern for accuracy. If you're going to burn paper with surplus ammo then it wont really matter. I typically like a faster twist so I can get "most" bullets to stabilize. I've personally found when I go with a slow twist I have a harder time running lightweight or boattail bullets.
    Last edited: Mar 18, 2011
  5. Shooter98

    Shooter98 Member

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    Also, if you're looking at a chrome lined barrel, good luck burning that barrel out. A stainless will last quite a long time. The only ar barrels I've ever seen wear out are surplus or non lined barrels.
  6. SON*OF*LIBERTY

    SON*OF*LIBERTY Active Member

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    barrel wear is not related to twist at all, nor should it be a priority on an AR-Style rifle, common consumers rarely fire enough rounds in a rifle's life time to replace it. CL is also overrated for this purpose.

    I would always start by focusing on the purpose of the rifle you are building... this will determine two things, The type of round to be fired in most cases, and the distances to be zeroed. Is heavy penetration necessary, or will you be trying at targets over distance.

    In General from my experience:

    Shorter the barrel, the lower the twist the heavier the bullet ,the better the penetration on average to close distances. (id say50-150yrds).

    Longer the barrel, the higher the twist, the more tightly the shot , longer the distance using lighter rounds resulting in lower penetration.

    Thats why DMR (Heavier loads at 150+ yards) and CQR (fragmenting rounds at short distances 50 and under) are very specific applications of the AR style platform.

    Common proven formula: 16inch 1:7 running m855 is a traditional and trustworthy setup. Accurate at good distance, with acceptable penetration. (lighter .223 target rounds will suffer) it is truly in the middle when you take the extremes in to account, and not the average.

    This is just my opinion, as thoughts on this subject vary widely
  7. madcratebuilder

    madcratebuilder Well-Known Member

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    [​IMG]
    PDXSparky and (deleted member) like this.
  8. Spitpatch

    Spitpatch Bronze Supporter Bronze Supporter

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    Nope. Does it for me! Wait.....wait...oh, yeah: Got any more nice 99's?
  9. Blitzkrieg

    Blitzkrieg Well-Known Member

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    Thanks for the replies.. this is for my gal, she already has a CAR15 and this one will mimic the size and weight for easy transition to the new gun. She will primarily be punching paper/bowling pins and taking a few courses with me starting with Appleseed, then later a Magpul course. Primary target ammo will be my reloaded M855 and hollowpoints not to exceed 70 grains, same types as our factory storage ammo. I would also like the gun to be able to fire 55 grain pills well in an emergency, as this will be one of her SHTF rifles if it proves reliable. My suspicions are confirmed by your comments and my web search yesterday, I need the 1 in 9 twist. The barrel I am looking at in the Yankee Hills 1/9 diamond fluted 16 inch carbine barrel with chrome lining. The rail handguard I have is the 6.5 inch and few barrels excepting M4 config seem to use that these days. I also need to keep it light as she's not a big girl. Comments by those with experience (good/bad/ugly) with that barrel, welcome. Chrome mainly for it's greater wear and anti corrosion nature in a SHTF situation where she may not give it the best care, and that I cannot find a suitable SS barrel in the medium/light carbine config

    We also have army .22 lr conversion kits and for Appleseed and plinking, she will sometimes use one

    I guess I'll just have to wait till they make the next run of these barrels in 1/9. Here's a pic

    [​IMG]
  10. supergenius

    supergenius Active Member

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    I almost bought that barrel in 14.5". Had no trouble finding them about the netz for 200 ish....

    Ended up with a custom Stainless 1:8 14.5" though as i got a rediculous deal on it. Ill find out the guys contact info that did my SS barrel, hes in Moses Lake IIRC, I gt a realllly nice deal on it from Skip at J&S. In fact I just loaded up my junk and Im going to shoot it right now :O) Good luck.
  11. Blitzkrieg

    Blitzkrieg Well-Known Member

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    Thanks. Yes, the one barrel I want seems to be the most popular and it's recently sold out everywhere. I did a 15 page Google search yesterday with none to be found in stock
  12. mjbskwim

    mjbskwim Well-Known Member

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