Barrel twist and suppressor thread handedness

Discussion in 'Advanced Gunsmithing & Engineering' started by GenePoole, Feb 11, 2018.

  1. GenePoole

    GenePoole

    Joined:
    Jan 8, 2017
    Messages:
    134
    I've got a SIG P239 barrel a friend want's threaded for a suppressor mount. It's about 3/4 inch longer than the factory barrel. The factory SIG setup for this, as I understand, came with a 13.5x1.0mm LH thread. I practiced a few of these from the AAC print(1) on some stock and was confident I could do the job. He gave me the gun and new barrel (it needed some fitting too) and while examining the two barrels, I noticed that the handedness of the rifling of each was opposite. The new barrel was of unknown origin, but marketed as unthreaded so as to use a more convenient thread such as 1/2-28 (Right-hand).

    In short, is there any relationship between the handedness of the rifling and that of the suppressor threads that I need to account for?

    1. http://www.advanced-armament.com/assets/images/pdf/manuals/ThreadGuideREV_01-040513.PDF
     
  2. Dusty Stevens

    Dusty Stevens

    Joined:
    May 8, 2014
    Messages:
    4,511
    Ive noticed half the pistols of european toots have lh twist barrels. I dont think it matters as i have an HK usp tactical that has a thread one way and a mark 23 which is the exact same model except their higher end that has the opposite threads. Both are metric and both have lh twist barrels just opposite threads. Maybe its a mil spec type thing over a consumer model in who makes the military suppressors and what thread they have
     
    JRS likes this.
  3. orbitup

    orbitup Silver $$ Contributor

    Joined:
    Apr 25, 2016
    Messages:
    29
    I have barrels with both kinds of threads. As long as the piston fits it'll work.
     
  4. carlsbad

    carlsbad Details matter. Silver $$ Contributor

    Joined:
    Mar 2, 2013
    Messages:
    1,542
    I don't know for sure, and don't want to research it since threaded barrels on pistols are illegal in CA, but it might be that you want the twist on a barrel opposite the threads on the suppressor so that the torque from the bullet going down the tube tightens the suppressor rather than loosens it. So for right hand thread I'd use a left twist barrel.

    --jerry
     
  5. butchlambert

    butchlambert Site $$ Sponsor

    Joined:
    Jan 18, 2005
    Messages:
    5,430
    My latest Rim Firebarrel is a LH tw.
     
  6. JRS

    JRS Silver $$ Contributor

    Joined:
    Mar 3, 2008
    Messages:
    5,620
    Right or left makes no difference. The suppressor isn't going to unscrew itself.

    The bullet doesn't touch the suppressor.
     
    Last edited: Feb 12, 2018
    TimS and DickE like this.
  7. Eddie Harren

    Eddie Harren Gold $$ Contributor

    Joined:
    Jan 22, 2006
    Messages:
    2,509
     
  8. butchlambert

    butchlambert Site $$ Sponsor

    Joined:
    Jan 18, 2005
    Messages:
    5,430
    I don't have a suppressor, my LH will just tighten the tenon. Hopefully it won't unscrew itself and fall off.
     
  9. Dans40X

    Dans40X Welder

    Joined:
    Nov 27, 2004
    Messages:
    1,293
    OP,
    Tell your buddy to purchase a 239 Bbl from SIG SAUER that is threaded 13.5x1LH & is a direct replacement w/adapters/thread protector, that will drop into the slide for $230 & there are currently 9 on hand at SIG SAUER.
     
  10. GenePoole

    GenePoole

    Joined:
    Jan 8, 2017
    Messages:
    134
    Where's the fun in that?

    It's done anyway.

    [​IMG]

    [​IMG]
     
    sdean and hpshooter like this.

Share This Page