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Posted: 3/10/2003 3:30:00 PM EDT
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I need to remove and replace my barrel,If I recall correctly I need to torque it to a specific value,then release,then retorque to a slightly higher value ,release then retorque to it`s final value and tighten further if neccessary to get gas tube clearance. Please verify that this procedure is correct and let me know what the proper torque values are. Thanks a bunch, Bossman |
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Min 30 ft-lbs, and as much necessary to align the nut, not to exceed 80 ft-lbs. Proper procedure is to lube the threads with anti-sieze (moly paste, generally), torque to 30 three times and back off, then torque to 30 and on up to max 80 to align the gas tube notch on the nut. If the nut won't align within the 30-80 ft-lbs range, you're supposed to try another barrel nut or barrel/upper combo; or you could try shaving or shimming to achieve proper notch alignment within the allowed torque range. |
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To clarify, the purpose of the three times torquing is to smooth the threads and get an even fit. Use moly grease (ordinary wheel bearing grease is fine) on the threads. Once you have a MINIMUM of 31 ft-lb, check for gas tube clearance, and continue to tighten until the next available notch lines up and allows the gas tube to enter, with equal clearance on both sides. Do not back off to get the gas tube to fit. The shank end of a 1/8" drill bit can be used as a tool to check for gas tube clearance. There is no magic figure where everything works right. It is just a matter of a minimum torque to insure it will stay tight, alignment of the gas tube, and a maximum figure, over which will cause it to strip the threads. |
| Here at work we have a product we buy that lists torque values with different lubricants. The torque values for moly are listed at half of those for traditional lube. 30 to 80 is a huge spread. My question is does the 30 to 80ft-lbs take into consideration the low coifitiant of frinction that the moly uses, or is it a rough rule of thumb thing? My point is that lets say to make things line up you have to go all the way 80ft-lbs with moly. The stress induced could be equal to 160 ft-lbs with regular petrolium based lube. This may be a little high for aluminum. Without studying this further I would say if using moly try to keep to the lower end of the torque spec. Just a little food for thought. |
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Yes, Moly grease is he recommended grease for this. I would have to see your product (whatever it is), and see why there is such a spread of torque readings. It may or may not be applicable in this case. When you first torque to 31 ft-lbs, after the two initial times, and then procede to go further for gas tube insertion (you only have to go another 1/2 notch at the most), you seldom have to exceed 50-55 ft-lbs. |
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