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Posted: 8/8/2004 6:59:31 PM EDT
| When reinstalling an AR15 barrel how much torque should be used on the barrel nut? |
| My TM 9-1005-319-23&P says 30 ft/lbs. Note: three times torquing procedure provides for a better fit and prevents barrel nuts from becoming loose. Apply molybdenum disulfide grease to the threads before installation. I torque to 30 pounds and then more to turn the gap to fix for the gas tube. |
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Use a good solidly mounted vise. No wussy vise, a manly vise!!! I recommend you use an action block, NOT barrel vise jaws. Make SURE you use the included insert (which slides into the upper like the bolt carrier. Moly grease--usually ordinary wheel bearing grease will contain moly disulfide. If you can't find "moly grease", just ordinary grease as is used in a grease gun is fine. Do not use NeverSeize. 30 ft-lbs is the minimum. There is no magic figure that is correct. Once you reach 30 ft-lbs, however much more it takes to align the nut for insertion of the gas tube, it takes. As stated above, just keep going until the notch aligns allowing the gas tube to be inserted and not touch on either side. Put the gas tube in, and wiggle back and forth. See if it swings approximately equally to each side. If so, cool. Done. |
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In rare instances, the barrel nut may not align before you hit 150 ft-lbs of torque. If this is the case, a different barrel nut is recommended, or mate the barrel with a different receiver. Or just exchange the barrel assembly for another one. In an armory situation this is a practical solution, but if you're dealing with one barrel and one receiver, it can be problematic as most people don't want to pull the sight tower off the barrel, which is necessary if you're to change out the barrel nut. CJ |
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What I used do is torque up to 25 (if I get alignment at 25, I leave it there) or so, remove the torque wrench and change it out for a long breaker bar. But you can easily feel when it is tight enough, so I just skip the torque wrench, and go for alignment. But the manuals almost imply that if you were to just get 41.385 ft-lb it would all be perfect. There is just no way to manufacture it to do that. And you can only put so many notches on the barrel nut, they have a lot already. What really happens, once you achieve minimum needed, and you continue to tighten to alignment, you are really pulling the aluminum forward, the soft aluminum distorting, allowing the nut to continue to turn. And this is good, it allows you to accomplish what you need to do. You would play hell trying to get alignment with a steel upper. |
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