Need help with barrel threads

Discussion in 'Gunsmithing' started by cr30378, Oct 8, 2018.

  1. cr30378

    cr30378 Well-Known Member

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    I had a gunsmith thread 3 barrels. He said they are 5/8-24 and the other 1/2-28. The issue iam having is the muzzlebreaks will not screw up on the threads, they will go about two rounds then get way too tight to go any more. Its like the threads on the barrels are not cut deep enough? What type of die would i need to fix this? I dont know much about dies so i need help. Some say unef on the die and some say unf, i dont know what to buy?I measured the dia. Of the threads and they are very close to 5/8 and 1/2 inch.
     
  2. J E Custom

    J E Custom Well-Known Member

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    First make sure the brakes thread pitch is 24 TPI and 28 TPI and also the tenon threads.

    If he used a Lathe to cut the muzzle thread tenon they should be right. If he used a die nut they probably are not correct.

    Buy a thread pitch gauge first, (They are much cheaper than a tap) . If the pitch is right, take your barrels back to the smith and have him fit the brakes to the muzzle tenon on the lathe.

    Taps and dies are/should never be used on a critical fit like this.

    J E CUSTOM
     
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  3. cr30378

    cr30378 Well-Known Member

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    Thanks
     
  4. cr30378

    cr30378 Well-Known Member

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    Now he is claiming the threads are 1/2-20 . Is their a anything i can do to fix this are is my barrel just useless ?
     
  5. J E Custom

    J E Custom Well-Known Member

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    Wow !! That is a standard 1/2 " thread pitch and Very few gun parts fit that pitch.

    He must have used a die nut In stead of the lathe. The best thing to do is find a real Smith and have him cut the thread tenon off and re thread with the correct thread pitch. It wont hurt the barrels velocity much if any and it will be done right.

    I would volunteer to build you a couple of brakes with the correct threads to fit his, But I would be afraid to attach anything to them.

    Fix the problem, not the symptoms and you will be glad you did. We all hate to give up any barrel length, but the added length with the brake will offset the loss.

    J E CUSTOM
     
  6. nmbarta

    nmbarta Well-Known Member

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    cut your barrel back and have it re crowned and threaded properly

    I personally wouldn't buy a brake and install it on a previously threaded barrel. If you have a side port brake it will need to be timed by the gunsmith anyway.

    If your using a radial brake that doesn't need timed, I still like the smith to make sure it's centered up properly. There isn't much clearance for that bullet, so if there was a slight mistake made to either the barrel or the brake, your bullet can contact the brake. As J E said, this is a critical fit, the tolerances are very tight compared to anything cut with tap and die.

    Installing muzzle brakes is a gunsmiths job imo.

    Which brakes do you have?
     
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  7. cr30378

    cr30378 Well-Known Member

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    Apa micro bastard 300 wsm, Precision armament m41 338 rum , tromix tank tank brake.458. Thanks for all input, iam kinda sick to my stomach right now.
     
  8. shortgrass

    shortgrass Well-Known Member

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    I thread barrels for muzzle attachments on a regular basis. I insist on have the muzzle attachment in hand to insure correct thread/pitch, and to insure proper alinement.
     
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  9. tobnpr

    tobnpr Member

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    I'm with ya...
    "Theoretically", one should be able to thread to Class 3 spec and not have the device.
    But " theoretically" never works well for me. Brake or receiver, I've seen more than a couple of thread-milled "precision" mass produced parts that were out of spec.
    I use full profile inserts and cut 'till it fits correctly.
     
  10. shortgrass

    shortgrass Well-Known Member

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    You can never know for sure what "class" of threads are in the muzzle brake or how far off the receiver threads are without having the parts in hand.
     
  11. cr30378

    cr30378 Well-Known Member

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    Can anybody tell me the distance of a properly threaded barrel from the back base of the threads to the muzzle?
     
  12. cr30378

    cr30378 Well-Known Member

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    Sorry on a 5/8-24 thread
     
  13. shortgrass

    shortgrass Well-Known Member

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    The length from the shoulder to the muzzle depends upon the muzzle attachment. I have seen different lengths on different brands of muzzle breaks. On most suppressors and suppressor attachments, where you attach the suppressor in a "quick release" device that stays on the barrel, the threads are .625" from muzzle to shoulder where it seats. Most muzzle brakes fall somewhere between .600" and .650". Just another good reason to have the brake in hand before threading the barrel. Everybody and their dog make muzzle brakes and it would be nice to have a standard to go by in both class of thread and length of threaded tenon, but no such 'luck' currently. Why are suppressors and the attachments standardized at .625"? Probably because the threaded length of the muzzle on AR platforms is .625"...………...
     
  14. cr30378

    cr30378 Well-Known Member

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    Ok i was just wondering if the dam guy messed that up to. He did. Thanks