1/2-28 threads for a 7mm mag muzzle brake?

Discussion in 'Gunsmithing' started by upjeeper, Jan 20, 2012.

  1. upjeeper

    upjeeper Well-Known Member

    Jun 5, 2005
    i've read at least one person does not recommend using 1/2-28 threads on any calibers larger then 6mm. was wondering if anyone could clarify. is there concern that there's not enough strength in those threads and it's better to go to 9/16-24 or 5/8-24 would give more strength due to a bigger diameter (and more thread contact then)?

    thanks for the advice
  2. KRP

    KRP Well-Known Member

    Dec 25, 2007
    I would say the concern is not the strength of the threads but the strength of the barrel. .456(minor diameter of 1/2x28 threads)-.284=.172/2= .086 barrel wall thickness. I'd use a larger diameter thread.

  3. ken snyder

    ken snyder Well-Known Member

    Jul 26, 2010
    Why stick with fractional sizes? Make your own diameter threads based off of what makes sense for the barrel!
  4. J E Custom

    J E Custom Well-Known Member

    Jul 29, 2004
    I would recomend using the largest thread Diameter possible that will leave a shoulder to seat
    the brake on and a realy good thread fit.

  5. Coyboy

    Coyboy Well-Known Member

    Jan 30, 2005
    We would always prefer the largest thread tenon possible. But in reality the guy who brings in his light weight 338 with a .595 muzzle is going to get a 1/2x28 tpi, or get it magna ported, which is a poor recoil reducer compared to most screw on brakes.

    I have put on some 1/2x28 thread brakes on a couple 338s and the customers have had no issues to date.

    Any body with a carbon wrapped barrel likely has 1/2x28 threads under the barrel end cap, this is a standard with many of the wrapped barrels. It allows a 5/8x24 thread to be installed on the cap for a brake thus creating two thread joints on the muzzle.

    If your barrel dia. allows it Try and choose the largest thread available for the brake you want, but I wouldn't lose any sleep on a 1/2x28 on a 7mm.
  6. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

    Jun 12, 2004
    If they are questioning the strength of the 28 tpi threads, there is no merit to it, I use 28 tpi threads on all of my Painkiller muzzle brakes and if fitted properly, they will handle anything you can throw at them and thats including the 408 CT class chamberings.

    If they are talking about the thickness of the barrel wall then I could see more reason to worry but even then, I have put several 1/2"x28 tpi threaded brakes on 7mm rifles with no problems at all, infact I have one on my 7mm Allen Magnum right now and it has about 700 rounds down it and no problem at all.

    It all comes down to a very quality fit and I do not put a thread relief on the barrel after the threads which further weakens the barrel threads, use a thread relief on the brake threads if you need one.

    Obviously, you want to use the larger diameter threads that your muzzle diameter will allow, especially with a button pulled barrel as the bore diameter will increase in size the more you turn the OD down.

    I have never seen a problem with 7mm with 1/2" threads. 30 cal would start to worry me.