AR-15 5.56 Questions

Discussion in 'AR-15 Discussion' started by rcb, Nov 1, 2008.

  1. rcb

    rcb New Member

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    First time poster on Firearmstalk forums. Hi @ all

    I am thinking about buying an AR-15 5.56 and I have some questions.

    1) Is it legal for a civilian to have a barrel shorter than 16"?
    2) Is it legal to hunt(Deer) with a small 5.56 cartridge?
    3) Is it possible to swap the upper assembly from a 5.56 to a 7.62 without changing the lower assembly?

    My next set of questions are more technical.

    4) What are the differences between 1x7, 1x8 and 1x9 twist barrel?
    5) What are the general purposes of these different barrel types?
    6) What gain cartridge should you use for these different barrel types?

    Thanks in advance!
     
  2. rcb

    rcb New Member

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    I am thinking about buying an AR-15 5.56 and I have some questions.

    1) Is it legal for a civilian to have a barrel shorter than 16"?
    2) Is it legal to hunt(Deer) with a small 5.56 cartridge?
    3) Is it possible to swap the upper assembly from a 5.56 to a 7.62 without changing the lower assembly?

    My next set of questions are more technical.

    4) What are the differences between 1x7, 1x8 and 1x9 twist barrel?
    5) What are the general purposes of these different barrel types?
    6) What gain cartridge should you use for these different barrel types?

    Thanks in advance!
     

  3. junho806

    junho806 New Member

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    1)you can get a shorter barrel legally...you just have to do some paper work, wait, wait, wait some more, then pay a $200 tax
    :rolleyes:
    2)sure why not? it'll be a little hard though haha
    3)because the 7.62 round is longer than the 5.56 you'll need a special lower as well i believe
    4)the difference is the rate of twist. the most common is 1x9 but it depends on preference
    5)not too sure...i just know most people prefer 1x9
    6)well for 1x9 barrel a 55gr works best not sure about the others

    hope that helped even though i didn't answer all of them
    :D

    welcome to the forum btw
     
  4. bkt

    bkt New Member

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    Hi and welcome!

    These depend on your local laws. There are AR "pistols" with very short barrels.

    It is not uncommon to have a 14" barrel with a 2" muzzle break to bring the total length to 16". That's the minimum here in New York.

    As for hunting deer, it's a pretty light round to use, but it will take a deer down.

    I believe so, as in this case.

    Just the rate of twist the bullet has per inch. 1:9 is a full turn in nine inches, for example.

    To accommodate different weight bullets and probably different loads.

    The 1:7 twist is standard military, I think. That's what's used for heavier bullets (75 to 77gr). Not sure about 1:8. 1:9 are very common for ARs and accommodate weights from 45gr up to at least 62gr. I've had very good results with both 55gr Remington (.223) and 62gr SS109 (5.56).
     
    Last edited: Nov 2, 2008
  5. bkt

    bkt New Member

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    A 7.62x39 is actually shorter than a 5.56x45.

    You might still be right...not sure how a 7.62x39 would feed with a stock lower.
     
  6. rcb

    rcb New Member

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    Thanks for the post reply!

    So, the projectile does one full rotation in nine inches? Or it rotates nine times per inch?
     
  7. rcb

    rcb New Member

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    Thanks for the post replies, This info has helped a lot!
     
  8. vegasjeepguy

    vegasjeepguy New Member

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    5.56 lower will not accept 7.62(x51) mags
     
    Last edited: Nov 2, 2008
  9. Ram Rod

    Ram Rod New Member

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    1) Is it legal for a civilian to have a barrel shorter than 16"? yes, so long as there is a pinned and welded (permanent) muzzle brake or flash suppressor to bring total length to 16", or get an NFA weapon following the proper paperwork and paying the transfer fee.
    2) Is it legal to hunt(Deer) with a small 5.56 cartridge? Depends on your local laws, for the most part, I don't think it's legal anywhere to use FMJ ammo for hunting
    3) Is it possible to swap the upper assembly from a 5.56 to a 7.62 without changing the lower assembly? yes...you can buy a complete 7.62x39 upper for your lower and buy the correct magazines for it (DPMS I believe)....it won't accept regular AK magazines

    My next set of questions are more technical.

    4) What are the differences between 1x7, 1x8 and 1x9 twist barrel? the difference in twist rates pretty much dictates the accuracy and stability of the preffered bullet according to bullet weight. The 1/9 twist should stabilize most bullet weights you'll be buying commercially More info here: http://www.gunnersden.com/index.htm.rifle-barrel-twist-rates.html
    5) What are the general purposes of these different barrel types? Please refer to the previous question/reply
    6) What grain cartridge should you use for these different barrel types? Please refer to Q/A #4 and the link supplied

    Thanks in advance! No problem.....you're welcome
     
  10. Ram Rod

    Ram Rod New Member

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    1/9 twist rate will spin the bullet one 360° revolution in 9 inches.
     
  11. Ram Rod

    Ram Rod New Member

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