Cutting down a fluted barrel --Muzzle thread Issue

Discussion in 'Gunsmithing' started by AKdan, Sep 21, 2018.

  1. AKdan

    AKdan Well-Known Member

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    Hi-

    I would like a shorter barrel for use with a suppressor. I have a 28" fluted palma barrel in .338. The diameter of the barrel at the valley of the flute at 20" is approximately .608". The challenge I am having is finding a threat that would work. 5/8 -24 major diameter is ~0.624". This would leave 6 small grooves in the threads where the flutes are, only about 0.016" deep. Minor thread dim being ~0.574" means there would still be continuous thread but might not make complete contact. A 9/16-24 thread only leave a wall thickness of 0.0875" at the minor threads, which is a little too thin. I may run a QD suppressor brake as to limit the number of times I thread on and off. Would a smith be able to do this or am I out of luck? What are your thoughts?

    Thanks

    Dan
     
  2. phorwath

    phorwath Well-Known Member

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    Not a gunsmith, but I would thread it over 1/2" length with 5/8-24. Seal threads with the weaker loctite (purple), and run it. These threads aren't under any heavy load. They just need to be sufficient to mount the suppressor or adaptor concentric with the bore, hold it tight under light to moderate torque, and seal off gases. Your barrel threads should be more than adequate.

    Barrel steel is soft. Should be easy to cut threads in a lathe. Even skipping across the fluting cups. FYI, I've never run a lathe in my life. But I've watched a bit... :confused:

    I used blue loctite on one of my brakes one time. Too difficult to unthread! Never again for me. Only low strength purple from now on.

    Well, let's see what the gunsmith's have to say about it...

    I'm just trying to get one of them revved up.:)
     
  3. phorwath

    phorwath Well-Known Member

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    So you'll have a little less than 0.017" thread engagement in the bottom of the flutes, correct? [(.608" - .574")/2] = 0.017"

    Find a gunsmith and get on with it. Seal the threads with purple loctite. No blowback anticipated over the length (~1/2") of these threads. That would be the only possible problem. And thread sealer will prevent it.
     
    Last edited: Sep 22, 2018
    just country likes this.
  4. AKdan

    AKdan Well-Known Member

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    I am going to be making some calls on Monday. I have a few barrels to get threaded, and 2 cut and threaded. Feel like I am keeping these guys in business.
     
  5. phorwath

    phorwath Well-Known Member

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    What ever became of cutting back your fluted barrel? Git'r done or go another direction?
     
  6. AKdan

    AKdan Well-Known Member

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    I had it cut down to 22”. Was just enough to have a little over .1” of wall thickness at the bottom of the lowest flute. Interestingly the flutes were not cut perfectly concentric to the bore. 2 were slightly deeper than the rest and there were the only 2 that interrupted the threads. I haven’t shot it since I got it back been traveling for work a bunch. Hoping to see how it goes this weekend. Hoping it’s not much louder now.