Muzzle threading

Discussion in 'Gunsmithing' started by Demon061, May 30, 2015.

  1. Demon061

    Demon061 Well-Known Member

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    So my brother bought a muzzle brake for his .300wm but die to its incredibly thin barrel (Winchester model 70 shadow, it's .575" thick at the muzzle) at the recommendation of the vendor he bought it from he bought a 1/2" threaded muzzle brake. Now, that leaves .134" of barrel wall between the groove And the... Atmosphere. At the behest of a local gunsmith we didn't thread it, and it looks like we might be sunk on the idea of a brake for this rifle. I was told that a general rule of thumb for muzzle threading is .5" for .223, 9/16 for 6.5 or .270, and 5/8 for .308. This all holds true I imagine?

    Thanks fellas.
     
  2. Edd

    Edd Well-Known Member

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    My arithmetic says the thickness is about .134" right now and if you put a 1/2" threaded brake on it the thickness will be about half that much. J E Custom, a member of this site and a Gunsmith, recommends a minimum thickness of .150".
     
  3. mountainman56

    mountainman56 Well-Known Member

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    Yeah that's pretty skinny. You might look into some of the clamp on brakes. I have not used them but others have posted on here with good luck.
     
  4. J E Custom

    J E Custom Well-Known Member

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    That Is what I recommend based on all the information I could get from barrel makers and engineers.

    There are some that say they have a 1/2"x28 tpi on there 30 cal and have not had any problems.
    But if they had a problem it would be bad so it is not worth the risk in my opinion.

    All though I don't like the looks of a clamp on brake, this would be a good alternative.

    Hear is a link to the FAQ section of my web site that will explain why. (The last question in the section)

    www.jecustom.com - FAQ's

    Hope this helps

    J E CUSTOM
     
  5. engineer40

    engineer40 Well-Known Member

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    I have a Witt Machine clamp on brake on a cheap rifle. It does seem to work to reduce recoil, which I'm assuming is your main objective. Although every time I see the bolts holding it onto the barrel, I wish I was looking at something else. Just not attractive in my opinion.
     
  6. Hired Gun

    Hired Gun Well-Known Member

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    Over the last 6 years I have probably installed a couple hundred 1/2-28 brakes over 30 cal. Not ideal but have yet to have an issue. Might be because of the very tight thread fit we use. Compared to the pressure at the breach the very tip of the muzzle has minimal pressure. These lightweight 300 magnums are the ones that need a brake the most.
     
  7. IdahoCTD

    IdahoCTD Well-Known Member

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    The only other thing you can do is thread it long and have a barrel nut made for the brake like Savage does for their barrels. That way you can run a 9/16x24 thread. I've done hundreds of 1/2x28's on .30 calibers without issues as well too.
     
  8. FEENIX

    FEENIX Well-Known Member

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    That's interesting!
     

    Attached Files:

  9. mountainman56

    mountainman56 Well-Known Member

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    +1 What FEENIX said. Never thought of that but that's an excellent solution.
     
  10. J E Custom

    J E Custom Well-Known Member

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    Once again.

    The reason I don't thread a .308 barrel to 1/2''x 28 tpi Is = The Minor diameter of a 1/2''x 28 TPI
    thread is .457. The bore is .308. leaving a total of .148. divided by 2 to get the barrel wall thickness
    to the rifling makes the barrel wall .074 thick. (1/16 of an inch is .062).

    Even though the pressure is much lower at the muzzle (10.000 psi to 17.000 psi depending on the cartridge) I don't want to find out if a 1/16 th of a inch + .012 thousandths will hold up.

    Fractions to Decimals

    A good suggestion was the barrel nut and a larger thread. It may not look great but at least it
    would be a lot safer.

    Just a concern

    J E CUSTOM
     
  11. Demon061

    Demon061 Well-Known Member

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    Wow lots of replies
     
  12. Hired Gun

    Hired Gun Well-Known Member

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    You don't need to find out if it will hold or not. It's been done at least untold thousands of times and not one mention of a failure has ever hit the internet world wide. Considering some or most guys can't thread to a shoulder so they cut to a relief even deeper than the thread minimum. Not even the thinnest 300 Ultra mag can distort or blow one off. If it was going to be an issue certainly we would have seen at least one bulged barrel by now. If a Glock blows a mag out it get's spread around the internet so much you would think every Glock made blew up.

    I believe a muzzle brake adds a measure of safety to these thin barrels.

    #1: We are only talking trimming the barrel for .6" back. Not even the length of any hunting bullet.

    #2: The added support from the brake threaded over it when it's tightened compresses the barrel due to the wedge action of the threads makes it super supported making it much stronger than the original untouched muzzle was.

    #3 Then the brake acts as a vented guard that helps prevent getting dirt or snow in the muzzle which can definitely cause a barrel failure.

    This makes putting a 1/2-28 brake over 30 caliber a non issue.
     
  13. J E Custom

    J E Custom Well-Known Member

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    I hear what you are saying. But just because it has/is being done does not make it safe. I just cant see doing something that the barrel makers wont, and logic tells me not to. It would be simple to go ahead and do, and also much easier than turning someone down. But there are things I will not do for anyone and this is one of those.

    I have repaired barrels that the threads have failed for one reason or another and seen a few that blew the brake off. (Only the smith will normally see this because most don't want to post that they screwed up anyway).

    My safety concerns for the owner is always at the top of my list and anything that "I" feel is unsafe, I just wont do it. I personally don't want to experience first hand, any kind of rifle failure.

    If other people elect to take risk with others, That is there decision. I have only tried to warn people on this issue, Not impose it on them.

    So all I can say Is "Go for it and live with the consequences".

    J E CUSTOM
     
  14. Demon061

    Demon061 Well-Known Member

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    Hmmm