Home CMMG The Truth About Torque: Barrel Nuts

The Truth About Torque: Barrel Nuts

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In this video, I discuss principle of torque and how that applies to barrel nut installations. I’ve also provided two formulas to determine either the torque setting for the wrench or the actual torque applied to a barrel nut with the use of an extension.

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33 COMMENTS

  1. Wow! Aren't you a mathlete! Just tighten the damned thing, and K.I.S.S. As long as your barrel is reasonably tightened to your receiver without harming the receiver threads, and your gas tube lines up, you're gonna be fine.

  2. You have a window of 35 to 80 foot pounds. Torque to 35 loosen 35 loosen 35 loosen then set it to 40 and go until you can line it up or if it doesnt need lined up then its good. Its not a aerospace bolt on a space shuttle or tires on your car. Dont "Nuke" it like we said in the navy.

  3. steel nut connecting the steel barrel to the alum. alloy upper receiver………30 to 80 pounds. there is a reason for the spec. to be varied so much.That would be that it doesnt have to be so tight to stay in the correct position. hence the locking tab on the barrel locking into the slot in the receiver….Its All Good……Just use a cresent wrench and turn it till its tight, problem solved.Dont worry about head space as it will only be 3-4 thousands at the most…that is the way its designed …to be worked on in the battlefield with one or two tools….HAVE A GOOD DAY.

  4. LOL The whole [L(w) + L(e) x Cos(A)] / L(w) section is basically a correction that says mathematically: for the purposes of determining torque, the measurement from the center of rotation to where the force is being measured is the only part that counts. Which is very true. The Cosine of 90 degrees is 0 (i.e. 0% or none) and the Cosine of 0 is 1 (i.e. 100% or all). So L(e) x Cos(A) basically states that we're using some percentage of L(e) based on the angle and adding that to L(w) to get the true length of rotation, then dividing it by the length of the wrench to get the total applied adjustment for the wrench. Sometimes math is funny with regard to how true it is.

  5. Salutatins from GA! great vid! it made perfect sense to this math-head wanna-be builder. Thank you for taking the time & effort to explain this rationale….ps, your outtakes were enjoyable as well!

  6. Good information but a little confusing, I would think your angle would’ve taken from center axis of the wrench head and the centerline of the socket on the adapter/extension regardless of the shape of the adapter. It doesn’t make sense to square off the edge of the adapter, there is a frog in Alaska that freezes during the winter and while frozen the frog stops breathing, his heart stops beating, his palms are sweaty, knees weak, arms are heavy there’s vomit on his sweater already, moms spaghetti.

  7. Now lets stop and think for a second. You have a barrel that fits snug a nut with a lot of threads on it a gas tube going through the nut and also attached to a gas block that is secured to the barrel and a handguard of some time attached trust me that barrel nut is NOT going to come off and even if it comes loose it will only move a tiny fraction due to the gas tube so this torgue obsession is rediculous tighten it down till it is tight but still lines up with gas tube hole and go shooting . Save yourself a lot of unnecessary bullshit

  8. For non free-floated barrels, the barrel nut must be tight, but allow the gas tube to slide through. It must be left there, because it's impossible to tighten it enough to reach the next trough, regardless of the torque.

  9. Excellent video. The math made it undisputable to the naysayers Agree, with a 30 to 80 range torquing a barrel nut is not rocket science. Until you see a person on YouTube setting the wrench at 75 ft/lb and then using it at the wrong angle. Thanks.

  10. With all due respect to our poster, I don't think the length or angle of the extension affects the torque applied to the barrel nut.

    The torque applied to an object is the same anywhere you measure it. Imagine this thought experiment: Take two torque wrenches and attach the socket ends together rigidly. Then fix one wrench, let's say to a vice. Then apply a force to the free torque wrench, any torque. Once in a steady state, look at the torque reading of the wrench in the vice. You will see that the torque readings of each wrench are exactly the same, one opposing the other. Now fix the torque wrenches to the ends of a metal bar, the length does not matter. Then apply a torque to both wrenches. No matter how far apart these wrenches are, or their orientations to each other, the torque readings will be exactly the same or the whole system will spin.

    Thus the torque the barrel nut sees is exactly the same as the torque wrench shows, no matter how far apart the torque wrench and the nut are or the angles between the torque wrench and the bar.

    This is why barrel nut wrenches don't come with instructions to adjust torque readings, even though they come in different lengths. So just trust the reading on the wrench, it does not have to be calibrated.

  11. Do you know how many people you just destroyed?
    Here is how it works, place the barrel nut ,use a little locktite, torque the barrel nut down between 35 and 80 foot pounds, back it off a few times too stretch the threads then finish the final torque and you're done

  12. You know for the first 30 years of the M16/AR15 people had to get the Barrel nut right enough to get the gas tube through the nut… Not exactly an exact science…. And the shit worked fine lol I think you need more hobbies man

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