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Posted: 9/24/2013 11:58:12 AM EDT
| Is it really necessary to torque the barrel down? And I have seen anywhere between 35 and 80 lbs. |
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A Craftsman beam-style torque wrench can be purchased online for around $25-30 dollars.
The procedure for torquing the barrel nut is to stretch the threads of the barrel nut to help in preventing the barrel nut from loosening. The steps in the Technical Manual are to torque to 30 ft. lbs. then loosen the barrel nut, torque back to 30 ft. lbs. then loosen the nut again, and finally torque to 30 ft. lbs. Once the barrel nut has been torqued to 30 ft. lbs. for the third time, afterwards to get the gas tube to align between the teeth of a USGI barrel nut you are able to torque up to 80 ft. lbs. but are not to go over this maximum torque value. Also when aligning the barrel nut with the gas tube, you are not to back the barrel nut off to do so if needing to adjust the position of the barrel nut's teeth with the tube. Instead you must loosen the barrel nut, and then torque back to 30 ft. lbs; but not go over 80 ft. lbs. in aligning the gas tube between the barrel nut's teeth. This is because you counter what's referred to as "bolt stretch" of the barrel nut and upper receiver's threads if you do so. The phenomena known as "bolt stretch" is one of the reasons why bolts and nuts have set torque values for the various bolt grades. |
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