Suppressors  Surefire Barrel Threading Help?

robzap

Private
Minuteman
Jul 24, 2011
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0
59
TN
Hi all, after much grief I managed to get my hands on a Surefire muzzle brake adapter for a new rifle build. I can't seem to get any help from Surefire on how to thread the barrel though. The brochure they include with the MB762-401R adapter doesn't have the exact 'Barrel Thread Matrix' drawing for all of the dimensions. The threads are M18x1.5, that's no problem; it's the other dimensions that aren't spelled out in the brochure. My gunsmith is about to give up on me. Any help or advice would be appreciated. I was planning on putting a FA762MG can on it if I can get the barrel threaded.

I have a new Lilja barrel and I'd hate to hose it. In an email Surefire tells me that the barrel can be no more than .830 for the first 2.75" of the barrel.

What I really need is a good drawing of how the barrel should be prepped for this particular adapter and a picture of how the adapter and can go together.
 

KYS

BBN #1
Full Member
Minuteman
Oct 8, 2008
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Lexington, KY
Re: Surefire Barrel Threading Help?

I'm sure GAP, Surgeon, SAC or a number of other builders could send you some specs on how to do the job. Its basically thread the barrel then turn down the barrel for 2.5-2.75" rearward of the shoulder. That lets the brake slide back over the barrel.

Good Luck
 

CoryT

Gunny Sergeant
Commercial Supporter
Full Member
Minuteman
  • Mar 5, 2004
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    Paulden, AZ
    www.gunsite.com
    Re: Surefire Barrel Threading Help?

    I've got a PDF of the general matrix. From the shoulder of the thread, cut back 2.145" to a diameter of .749" +.000/-.005, the threads should be .625" with a 45 deg chamfer on the muzzle and the shoulder. A thread relief is not required, but is permissable.
     

    robzap

    Private
    Minuteman
    Jul 24, 2011
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    0
    59
    TN
    Re: Surefire Barrel Threading Help?

    Thanks Garin. I've give you a call in the morning. I appreciate the quick response and help.