barrel twist which one

Discussion in 'AR-15 Discussion' started by laynejc, Feb 11, 2009.

  1. laynejc

    laynejc New Member

    I am looking to get an upper and would like some input on the barrel twist. It will be a 16" carbine upper and I have a choice of 1:7 chrome moly or 1:9 chrome moly twist ratio. This will just be a plinker. Any suggestions would be great.
  2. robocop10mm

    robocop10mm Lifetime Supporting Member Lifetime Supporter

    I have both. The 1/9 should be good to go for anything short of 70 gr bullets. IF, you want to shoot 70+ grain bullets go 1/7.

    Either should be fine with the lighter bullets as long as you don't try to push "match" bullets too fast. The thinner jackets of the 50-55 grain HP's are likely to come apart at higher velocities (above about 3000-3100)

  3. Dillinger

    Dillinger New Member

    From previous experience, here is what we recommend around the shop:

    1:7 is not the best choice for the available bullet weights in common "retail" land....

    1:7 is a faster spinning bullet rate, which means you have to shoot the heavier bullets out of them ( probably in the 77 grain, or higher, environment ). Most of the common civilian and military stuff is either 55 grain or 62 grain. With a faster twist rate, and the right conditions like high heat and low moisture, you could very easily overspin a 55 grain bullet and get it to particl-ize ( I made that word up ) and therefor would be useless in the field.

    Now, if you were reloading, the 1:7 twist with the heavy bullets would give you great knock down potential over someone shooting the 55 grainers all day long.

    So, basically plus one on what Robo said. :D
    Last edited: Feb 11, 2009
  4. hillbilly68

    hillbilly68 New Member

    1:9 for the 16in "plinker". Leaves more effective options for you with factory ammo.

    Another +1 with robo and the fuzzy guy that used to be known as JD
  5. slowryde45

    slowryde45 New Member

    as stated above, IF you can find the heavier grain bullets in the new OBAMA-era, then I would go with the faster twist 1:7. that being said, you can still shoot the lighter rounds through it, just not the real light stuff.

    Or go with the 1:9 and have a decent twist rate for everything from 45gr varmint rounds up to about 75gr, and you'll be pushing it at that weight.

    OR...if you can find it, compromise and get the 1:8 twist and have the best of both worlds. :D