Out of spec threads issue

Discussion in 'NFA Weapon Discussion' started by Delasangre4231, Oct 6, 2018.

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  1. Delasangre4231

    Delasangre4231
    Oregon City
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    So I just went up and checked out my new silencer at the FFL and when we went to put the QD muzzle brake on we noticed it was really loose and sloppy on the threads. It did tighten up nice on the shoulder and was perfectly concentric with the bore. I gave it 30ft-lbs and we fired 10-15 rounds to check function. It didn't back off or anything.

    We measured the threads and the tops of the threads measure .612 and the chart he had said 5/8x24 is supposed to be .625, so it's a bit small.

    We are concerned that if it does come loose it will be sloppy enough to cause baffle strikes.

    So my question is will rocksett and a little extra torque be enough to hold it or will there be issues? Will the extra gap be a problem for the rocksett? Should I use a different host or get a new barrel?
     
  2. Delasangre4231

    Delasangre4231
    Oregon City
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    According to this the minimum is 0.6166, so my threads at 0.612 are not good

    Screenshot_20181006-164002_Chrome.jpg
     
  3. Kruel J

    Kruel J
    Orygun
    Moderator of the Coriolis effect Staff Member Lifetime Supporter Gold Supporter Silver Supporter Bronze Supporter

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    You might list the specs of your host/barrel.
     
  4. Delasangre4231

    Delasangre4231
    Oregon City
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    Its the factory barrel on my PTR 32P, supposed to be 5/8x24
     
  5. Kruel J

    Kruel J
    Orygun
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    Have you reached out to PTR?
     
  6. Delasangre4231

    Delasangre4231
    Oregon City
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    I just found out today and I think they are closed on weekends, its my first thing to do on Monday
     
  7. Used To Hunt

    Used To Hunt
    Lewis County
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    I would suggest measuring the pitch dia. If it is in spec for a class 3 fit I wouldn't worry much since you plan on using rockset... then again most suppressors end up costing $1000 and a 1 year wait so getting the barrel rethreaded is the safest bet. Sorry to hear you got a lemon
     
  8. Delasangre4231

    Delasangre4231
    Oregon City
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    I can't re-thread, its as short as it can get.
     
  9. Delasangre4231

    Delasangre4231
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  10. Delasangre4231

    Delasangre4231
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    Class 3 has a range of 0.625 and 0.617 and my threads are 0.612
     
  11. HB of CJ

    HB of CJ
    42.17N -123.64W ?
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    This is why a good can manufacture will want to shorten and thread PROPERLY both the host barrel and the can. Takes time. Costs money to do it correctly. Once the can is properly torqued on it should remain on the firearm in question. Our Elite Iron Cans thread on very tightly and slowly. No spinning on.

    Elite Iron Suppressors.
     
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  12. Used To Hunt

    Used To Hunt
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    Damn, my heart goes out to you even more now that I see what kind of firearm is in question. Also I said the Pitch dia not the major dia. The pitch dia is a better way of determining the engagement of the thread flank. If it was good and the O.D. was bad it might give one the confidence to let it ride.
     
  13. Delasangre4231

    Delasangre4231
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    The barrel is factory threaded by PTR, it wasn't cut down or re-threaded.

    I don't know enough about threads how to measure pitch diameter. I'll try and find out.
     
  14. Tornado-Technologies

    Tornado-Technologies
    Hillsboro
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    If you haven't already solved your problems - we have all the equipment to measure your threads, gauges threads mics etc. If you come in on a Friday I'd be more than happy to help you. Ask for Mike. We're in Hillsboro.
     
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  15. Delasangre4231

    Delasangre4231
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    Thanks, I got the gun back from PTR and the threads were tighter but still not what I'd like. But I went ahead and used rocksett and installed my muzzle brake. It is concentric with the bore, I tested with an alignment gauge and my silencer installed. And so far so good.
     

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