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Thread: minimum barrel dia for

  1. #1
    SD Regular bobjs's Avatar
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    minimum barrel dia for

    can anyone tell me what the minimum barrel dia for the 1/2" unf 20 tpi thread to be cut into.

    i just hope the end of my 308 barrel is thick enough

    bob.
    WARNING: LUPUS IS A KILLER, lets support them in the need to find out what it is, what causes it and how do we defeat it. Donating to LUPUS UK | LUPUS UK

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  2. #2
    On a 308, the 1/2" unef would be better. (1/2"x28tpi) gives you more wall section.
    1/2"x20 and 5/8"x18 seems to be a European thing. US seem to prefer 1/2"x28 and 5/8"x24
    which I think are better for the application.

    What diameter do you have?
    edi

  3. #3
    Anything over 9/16" is safe, but not sure I'd want a .308 hole in the end of a 1/2" thread, purely from a mechanical strength point.
    Probably be fine with an over barrel mod with rear bush, but not a muzzle can, only need a bump on a fence or stile to strain it.

    Neil.

  4. #4
    SD Regular bobjs's Avatar
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    cheers lads,

    the rifle is away for the night, just tucked it in with a hot chocolate and a tatty scone done in the toatster. so i will check it in the morning.

    bob.
    WARNING: LUPUS IS A KILLER, lets support them in the need to find out what it is, what causes it and how do we defeat it. Donating to LUPUS UK | LUPUS UK

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  5. #5
    Distinguished Member Ronin's Avatar
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    I wont do 1/2" UNF on .30 cals, better with M14x1mm if your barrel diameter is large enough.


    If not, do without,

  6. #6
    I am bemused by those who think a 1/2"x20UNF thread will automatically fail in some way on a 308.
    They pass proof well enough- and I had no trouble with the 2 or 3 308s I had so threaded.

  7. #7
    SD Regular bobjs's Avatar
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    i will ask my rifle smith hit thoughts as he will be doing it

    bob.
    WARNING: LUPUS IS A KILLER, lets support them in the need to find out what it is, what causes it and how do we defeat it. Donating to LUPUS UK | LUPUS UK

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  8. #8
    Quote Originally Posted by 20-250 View Post
    I am bemused by those who think a 1/2"x20UNF thread will automatically fail in some way on a 308.
    They pass proof well enough- and I had no trouble with the 2 or 3 308s I had so threaded.
    It won't fail in normal use, as for proof, well the pressure at that point is low so I wouldn't expect it to go pop.
    But mount a muzzle can that then gets a knock, well it's not held on by much is it.
    I snapped the threaded section from the end of an Anschutz .22lr, a plastic moderatror and a knock on a fence, next time I went to take a shot I had to go back and look for the moderator, funny thing is Annie muzzles are counter bored to the crown is behind the threaded section.
    The counterbore is, yes you guessed it. .300"

    Neil.

  9. #9
    I wasnt aware it was just barrel diameter that was important
    surely the calibre and the barrel diameter are taken into consideration

  10. #10
    SD Regular bobjs's Avatar
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    Quote Originally Posted by bewsher500 View Post
    I wasnt aware it was just barrel diameter that was important
    surely the calibre and the barrel diameter are taken into consideration
    you're correct big man, i will call Neil at lunch time (Mckillop rifles) to double check, i think as you ssay both the bore and the barrel diameter have to be taken into account. if it has to be 14/1 or another thread then so be it, it just means that i have mods that will fit it if it was 1/2" unf 20

    bob.
    WARNING: LUPUS IS A KILLER, lets support them in the need to find out what it is, what causes it and how do we defeat it. Donating to LUPUS UK | LUPUS UK

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