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Posted: 6/12/2011 6:43:37 AM EDT
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I read somewhere that when torquing a barrel nut that you should torque it to 30#s.
Back it up, torque it to 30#s again, then I lost the final torque poundage. 
I was thinking it was 60#s, but I am not sure. Anyone remember the final torque amount? 
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I believe the upper limit is 80 ft/lb, over torquing CAN have a negative and may cause extra windage, you don't need that.
As stated, use the rule of three... tighten and loosen three times to 30 ft/lb. Then tighten until you get the next tooth lined up which allows proper install of gas tube. And remember to use a little moly on the threads. |
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I am impressed!
You guys sure know the right answers. What sparked my question was that I read somewhere that there was a higher torque limit, but at the time I failed to read it carefully. Shortly after I posted my question, I realized that the barrel nut has to align for tube entry, but I did not know that 80#s was the upper limit. I appreciate your input and your answers. You guys are the greatest for sharing your knowledge. I'm on my fourth build. I have milled three lowers in house. My buddy has milled two of his own and we are going to build one of his this week. We both used DPMS upper kits and they seem to be very good and were reasonable in price. I put Adams Arms pistons on the two of mine and a 24" stainless bull on one. Again, Thank you for giving me the answer, I appreciate your kindness. If in NC, stop in for a chat. 
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I have worked at a machine shop for 8 years. I have NEVER had to tighten and loosen anything 3 times. I think someone that has some serious OCD has developed this strategy to putting a nut on threads. Do you tighten and loosen the nuts on your car wheels? No, you tighten to the recommended MFG torques setting. This is a nut holding a barrel that already is fairly snug. Oh, and don’t forget the grease – This will start a 40 page thread of arguments on type - Find the WHITE moly grease like they use on marine props - High temp, water impermeable, and doesn't promote corrosion.
If you actually tighten the nut to 30 ft-pounds and the hole just doesn’t align, 40 ft-pounds will normally hit the next hole without issue. 80 ft-pounds would probably get you 1 or maybe 2 more teeth. It has been stated on many sites that you should use the minimal torques setting for the maximum accuracy of the rifle. If you don’t believe it, then do some testing yourself. However, I have heard of dudes cranking to 80 ft-pounds and then backing off to hit the holes. When I hear that, I just say IDC – I Don’t Care...It’s their weapon. |
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Quoted:
I think someone that has some serious OCD has developed this strategy to putting a nut on threads. That would be the army: TM9-1005-319-23, Pg.3-41 On the other hand, they aren't totally OCD, a few pages previous advises that if the barrel is bent, "give the barrel a sharp jerk" and bend it back straight. |
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You want weird, check around about how to "regulate" a shotgun barrel so it will naturally point to where the shooter needs it. Basically, bend it the right way til you get there.
The 30-80 keeps a newly trained Armorer from ruining an upper. An competent mechanic knows what 30 or 80 feels like, he's tightened many a nut or bolt over decades, and broken enough to know when something isn't right. YOU all can tighten with a torque wrench as much as you need, some of us will just twist the nut with a pair of 18" channelocks and move on. |
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