Gunsmithing WTK: Castle nut torque - M4

spr1

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Re: WTK: Castle nut torque - M4

I have seen that in a couple of posts, but, that is around the correct torque for a #10-32 cap screw not something that big. The barrel nut is in ft-lbs, the buffer tube is in ft-lbs, all with similar size threads. Why would the Castle nut be approx 1/10 the torque? Am I missing soemthing? thanks
 

rijndael

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  • Jan 20, 2004
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    Re: WTK: Castle nut torque - M4

    I don't know why the specs are what they are, I just follow the directions.

    Here is another data point:

    http://zugzwanged.org/dat/weapons/docs/man/m16.pdf
    Page 200:

    ARMY TM 9-1005-319-23&P
    3-81.1

    CARBINE ONLY
    6A. Lubricate threads of lower receiver (5.1) and lower receiver extension (5.2) with molybdenum disulfide grease
    (item 19, app D) before reassembly.
    6B. Pre-position the spring (5.3) and buffer retainer (5.4) into the retaining hole of the lower receiver (5.1). Screw the
    locking nut (5.5) onto the lower receiver extension (5.1) with the three notches on the locking ring (5.5) facing
    forward.
    6C. Align the receiver end plate (5.6) onto the lower receiver extension (5.2) with the lug of the receiver end plate
    (5.6) facing forward.
    6D. Pre-position the takedown pin (5.7), detent (5 8), and spring (5.9) in lower receiver assembly (5.1).
    6E. Push down on the buffer retainer (5.4) and spring (5.3) and at the same time, screw the lower receiver extension
    (5.2) in until it retains the buffer retainer (5 4) in position.
    6F. Align the lug of the receiver end plate (5.6) into the rear of the lower receiver (5.1). Screw the locking nut (5.5)
    forward until it contacts the receiver end plate (5.6).
    6G. Using the special tool (Item 12, app C) tighten the locking nut (5.5) until snug.
    <span style="font-weight: bold">6H. Using the special tool (item 12, app C), and torque wrench, torque locking nut (5.5) to 40 ±2 inch pounds.</span>
    6J. Stake the receiver end plate (5.6) in 2 places across from the notches in the locking nut (5.5).
     

    Psywar1-0

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    Mar 5, 2005
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    Re: WTK: Castle nut torque - M4

    Why the difference, because one is staked and the other is not.

     

    spr1

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    Re: WTK: Castle nut torque - M4

    Staking prevents vibration induced loosening, but does nothing to mechanically preload the connection, which prevents fatigue failures and eliminates relative movement under load. Two very different things.
    I wonder if that manual from '87 has been updated. They did change the design of the nut.
     

    Psywar1-0

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    Re: WTK: Castle nut torque - M4

    Yes the manual has been updated, and is now restricted distro, only releasable to DoD and DoD contractors, not even other federal agencies.........