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Barrel nut torque question

Discussion in 'Black Rifle Forum' started by Cole125, Apr 21, 2013.

  1. Cole125

    Cole125 Silver Member

    7,584
    2
    Apr 5, 2008
    Far West, USA
    Buddy of mine is putting a new rail on his AR and needed to change out the barrel nut. His torque wrench goes to 25 ft/lbs max, and he said he got the barrel nut to line up perfectly at 25 ft/lbs.

    Is this tight enough for the barrel nut? I assume it is impossible for it to come loose because of the gas tube going through it. If it came loose could it bend the gas tube?

    I have read the barrel nut should be 30-80 ft pounds, is 5 pounds lighter enough to **** things up?

    Thanks
     
    Last edited: Apr 21, 2013
  2. WoodenPlank

    WoodenPlank Who?

    7,958
    3
    May 15, 2010
    NW Florida
    The nut isn't likely to back loose due to the gas tube, but an improperly torqued barrel nut CAN cause accuracy issues, as the barrel won't locked as tightly to the reciever as it needs to be. I'd imagine it could also lead to headspacing issues if the barrel has any fore/aft play.
     


  3. Cole125

    Cole125 Silver Member

    7,584
    2
    Apr 5, 2008
    Far West, USA
    Hmm well should he shoot it as is and see if there is any accuracy issues?

    I assume the proof is in the pudding, if he shoots and and it groups good hes good to go right?
     
  4. mjkeat

    mjkeat

    3,447
    3
    Jun 17, 2009
    Midwest
    I don't know, never half-assed it. I did research it a while back and according to good sources it could cause accuracy issues. I wouldn't shoot it until the job (assembly)was finished.
     
  5. Cole125

    Cole125 Silver Member

    7,584
    2
    Apr 5, 2008
    Far West, USA
    Got you, I'll tell him to take it to a smith and have it done correctly.
     
  6. K. Foster

    K. Foster

    2,511
    442
    Feb 19, 2002
    Mo.
    I believe it’s 30 to 80. Research it if you’re in doubt. I would get a proper torque wrench and do it right. What I was taught is go to 35lb, then 1 more notch. Get it tight. I wouldn’t worry about the 80lb maximum, you’re not likely to get there with out forcing something. Be sure to use the proper anti-seise grease and torque it, loosen it, re-torque 3 times.
    Do not shoot it until it's done right!!
     
  7. samurairabbi

    samurairabbi Dungeon Schmuck

    5,894
    39
    Dec 31, 1998
    Indianapolis, IN
    There is a way he can measure above 25 using his existing torque wrench.

    He can put a wrench extension between the barrel wrench and the torque wrench. Compute the ratio of the new assembly length to the torque wrench itself. That ratio then becomes a correction factor that can adjust the INDICATED reading to the ACTUAL exerted torque.

    Or he could just get another torque wrench.
     
  8. bullittmcqueen

    bullittmcqueen Gunfighter

    540
    0
    Feb 18, 2011
    Leesburg, GA
    Between 30 and 80 ft/lb is ideal. I would wager if he backed the barrel nut off and retorqued it several times and advanced it to the next "slot" it would be just right.
     
  9. faawrenchbndr

    faawrenchbndr DirtyThirty fan CLM

    36,121
    479
    Nov 24, 2005
    Troy

    Basically torque to 30, adjust torque wrench to 80 and tighten
    Just until the slot aligns with the receiver cut out for gas tube.
    If 80 is exceeded, loosen and start again.
     
  10. surf

    surf

    1,019
    4
    Jul 7, 2010
    I will note that the rifle might shoot fine for quite some time under torqued. Depending on how much he shoots, it might be good to go for the life of the rifle. Even under heavier use he might get away with it. But I can say that without a doubt if the barrel nut loosens just a bit there might be a tiny bit of movement that you may not be able to physically notice by wiggling the barrel, however your groups might be all over the place. I have fixed many a rifle that had a barrel nut that was under torqued.
     
  11. Jack Greenwell

    Jack Greenwell

    223
    0
    Dec 7, 2007
    Texas
    I have seen a barrel nut cut off a gas tube, it is actually common for our troops ( I am aviation not doorkicker). The situation is the one man (guy kicking in a door to kill bad guys) tenses up and while using as much force as possible to kick the door, some of that force transfers to you weapon hands. Without a FVG it is way hard to do but with one it is quite easy. If he knows how to do it he should just buy a better wrench for this project, it's cheaper than hiring someone.