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Posted: 1/31/2017 12:09:33 AM EDT
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2 A2 uppers, both surplus. One FN and one Colt. While installing the barrel nuts it seems I am lining up for the gas tube at a lower torque than with my other builds. I've built a few flat top uppers (new parts) and usually seem to end up ~ 50-60# ish , these 2 @ 35/41#.
Same procedure, same wrenches. Tighten to 30#, then back off, 3 x, then torque. AEROSHELL on all builds.New bbl nuts each time. Any insight? Could the fact that these 2 uppers have been used possibly several times over account for this? Also, trying for the next slot in the bbl nut seemed almost impossible on both, rather than damage anything I stopped, since I am in the specs. Albeit the low end. |
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When re-barreling an upper... I always use the calibrated elbow method.
Not knowing if the upper in the past was over-torqued or threads stretched... I try to avoid the "tighten until the threads strip out and back off 1/4 turn" method. While not the "proper technique" (tighten, release... tighten, release... tighten to a desired torque)... if it is not a new upper receiver, there would be some risk on a re-torque. |
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If you're meeting the appropriate torque requirements, I wouldn't worry about it. Also, if you're reading the torque directly off of the wrench (or using the click-type), you're already torqueing them further than is indicated.
One thing to consider is that the new finish covering the receiver and threads isn't terribly smooth most of the time, so that grit can provide some additional resistance. I would be curious to see if you had similar results if you tore down one of your others, and cleaned things up real good and started it over again. |
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Quoted:
If you're meeting the appropriate torque requirements, I wouldn't worry about it. Also, if you're reading the torque directly off of the wrench (or using the click-type), you're already torqueing them further than is indicated. One thing to consider is that the new finish covering the receiver and threads isn't terribly smooth most of the time, so that grit can provide some additional resistance. I would be curious to see if you had similar results if you tore down one of your others, and cleaned things up real good and started it over again. Can you explain this? |
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Quoted:
Can you explain this? Quoted:
Quoted:
If you're meeting the appropriate torque requirements, I wouldn't worry about it. Also, if you're reading the torque directly off of the wrench (or using the click-type), you're already torqueing them further than is indicated. One thing to consider is that the new finish covering the receiver and threads isn't terribly smooth most of the time, so that grit can provide some additional resistance. I would be curious to see if you had similar results if you tore down one of your others, and cleaned things up real good and started it over again. Can you explain this? He's assuming you're reading torque off the wrench while using an armorer's wrench on the nut. That wrench actually extends your "lever" by 1.5-2" (or more, armorer's wrench dependent) because of the offset nature of the tool. The torque wrench is calibrated at its pivot point, so you're actually applying slightly greater torque than what it reads. |
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Thanks for the input everyone.
I have no idea how many times these have been rebarreled, or even how far someone has wrenched them down previous. Didn't want to risk screwing them up by over tightening. I am over the minimum, so I'll roll with it. Thanks again. Tig |
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Quoted:
He's assuming you're reading torque off the wrench while using an armorer's wrench on the nut. That wrench actually extends your "lever" by 1.5-2" (or more, armorer's wrench dependent) because of the offset nature of the tool. The torque wrench is calibrated at its pivot point, so you're actually applying slightly greater torque than what it reads. That's correct. Most people don't realize that by putting an extension on a torque wrench that is not at 90*, you will over-torque the nut/fastener. The formula you use to prevent this is: (Torque X Length) divided by (Length + Extension). Here's a good explanation with diagrams: http://www.engineersedge.com/manufacturing_spec/torque_wrench_1.htm |
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