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Thread: .50 BMG Torque

  1. #1
    Join Date
    Feb 2019
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    .50 BMG Torque

    What is the normal torque value when installing a .50 caliber BMG barrel to a McMillan Action?

  2. #2
    Join Date
    Feb 2003
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    Houston, Texas
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    Quote Originally Posted by FBecigneul View Post
    What is the normal torque value when installing a .50 caliber BMG barrel to a McMillan Action?
    Francis, some years ago I helped the late Eric Klemitich install a 50 BMG Ackley Improved Barrel on a McMillan Action that had a 1.500 diameter thread. I think it was 12 tpi.

    He had no way of holding it, or a large enough torque wrench. I chucked the barrel up in one of my large lathe’s 4 jaw chucks to hold it. He had a rear entry wrench with about a 1 inch hex on the end.

    The torque he wanted was 150 ft pounds.

    Hope this helps.
    Last edited by jackie schmidt; 03-01-2020 at 05:20 PM.

  3. #3
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    Nov 2006
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    Augusta, Maine & Palm Coast, Fl
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    What about machinery's Handbook?

    Might tell ya what the engineering value is and then one could consider perhaps reducing it a bit. Likely google could help as well.

    My first real job was in an auto garage @ age 15. Whenever I'd ask the owner how tight he's say "about all that wrench will stand". Does that help any?

    Pete

    P.S. the chart I saw on Google sez 1316 to 1645 for a 1.50"-12 . If that's inch pounds it would be 109 to 137 ft/lbs. The chart shows some sizes with Ft Lbs and inch pounds. Likely the 109 would get it.. I used 50 Ft/lbs for years on my 30 barrels just to have a benchmark. Don't believe it stretched anything. I use 25 ft/lbs on .22 RF barrels.
    Last edited by Pete Wass; 02-29-2020 at 04:04 PM.

  4. #4
    Join Date
    Mar 2013
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    Boothbay Harbor, ME
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    Quote Originally Posted by Pete Wass View Post
    Might tell ya what the engineering value is and then one could consider perhaps reducing it a bit. Likely google could help as well.

    My first real job was in an auto garage @ age 15. Whenever I'd ask the owner how tight he's say "about all that wrench will stand". Does that help any?

    Pete

    P.S. the chart I saw on Google sez 1316 to 1645 for a 1.50"-12 . If that's inch pounds it would be 109 to 137 ft/lbs. The chart shows some sizes with Ft Lbs and inch pounds. Likely the 109 would get it.. I used 50 Ft/lbs for years on my 30 barrels just to have a benchmark. Don't believe it stretched anything. I use 25 ft/lbs on .22 RF barrels.
    I was told years ago that in either the Model A or T service manuals the length of the wrench was specified for torque. Don't know never read one but I'm guessing they figured the average guy could get X torque with a certain size wrench.
    Pete, an 8in wrench works just fine for rimfire barrels!

    Keith

  5. #5
    Join Date
    Feb 2019
    Posts
    412
    I forgot about the Machinist’s handbook. I tried here first. I also figured the 100 ft/lb area would be close.

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