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Posted: 1/21/2014 7:38:21 AM EDT
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Quick question. About to assemble an upper, got me to wondering what you guys do. Do you put locktite on the upper threads before putting the barrel nut on? Or just throw it on and torque it down? |
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The grease that is called for is a MIL-G-21164D compliant grease such as Royco 64 or Aeroshell 33MS. You can get Aeroshell 33MS from Umbrella Corp. for $3.00. This small container has enough to do several builds. If you decide to obtain something local to your area, a marine grade molybdenum disulfide grease will suffice.
When installing a barrel nut, place a light coat of grease to the threads of the barrel nut, and the threads of the upper receiver. Screw the barrel nut all the way on then wipe away the excess grease that piles up on the outer edges of the barrel nut. Here is the torque sequence that is in the M16/M4 Technical Manual. Set the torque wrench to 30 ft. lbs., and then torque the barrel nut. Now, loosen the barrel nut, and torque it again to 30 ft. lbs. Loosen the barrel nut one final time, and torque it back to 30 ft. lbs. If a barrel nut groove is not lined up for the gas tube to sit in at 30 ft. lbs; set your torque wrench to 80 ft. lbs; and slowly apply torque until the next groove lines up. It hopefully should not take up to 80 ft. lbs. to get the next groove to line up. 80 ft. lbs. is just the maximum amount of torque that can be applied when trying to get the next barrel nut groove to line up with the gas tube. My AR used a proprietary barrel nut, which I torqued to 35 ft. lbs. Finally, the reason for the torque sequence as explained in the technical manual for tightening and loosening to 30 ft. lbs. three times is to prevent the barrel nut from backing. Also make note, if you go past a groove when lining up for the gas tube when torquing the barrel nut, do not just loosen the nut to get it to line up. What I mean by that is only align a groove with the gas tube when tightening the barrel nut. |
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