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Posted: 6/16/2011 6:40:57 AM EDT
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Hey all. Got a problem. I'm doing a rebuild (AR of course). I going with a low end floating handgaurd. The barrel nut will not line up. I can get it tight but the gas tube hits just enough to not make it home. I back it off a smidge and it's good but I fear I'm not close to the proper torque spec. Close but my new wrench is in inch/lbs. so I'm guessing. I tried working it loose and then trying to get the next hole.(it's written on here that you should do this 3 times on a new build) I greased the threads and barrel end. No mater how I try I can't make the next hole.
Also I'm using a barrel vise that I made myself. used many times and loaned out to friends. if i crank on the wrench the barrel will twist in the vise. And believe me when I say the vise is tight.... What say you? good enough or bigger problem ? |
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Quoted:
When that happens to me, I apply a generous coat of moly grease, torque it on to 50 ft lb, back it off, torque it back on, take it off. Andfor some reason, when I torque it back on the 3rd time, it works- I honestly don't get the logic but it works. I did that ! I've done it with all my other builds and with the exception of one slightly mauled ring it worked everytime ! |
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Quoted:
I would get a ft/lbs torque wrench to see where your at on torque when the nut is tight .. under or over torqued can cause problems. Also you might need to lap the uppers face to get the nut to index properly. If I remove material from the face of the upper wount that affect headspacing ? |
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Quoted:
Quoted:
I would get a ft/lbs torque wrench to see where your at on torque when the nut is tight .. under or over torqued can cause problems. Also you might need to lap the uppers face to get the nut to index properly. If I remove material from the face of the upper wount that affect headspacing ? no, but i wouldn't do it anyway i've never had a barrel nut that didn't index within the 35-80ft/lbs range. especially using the the tighten, loosen, tighten method. |
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if your home made upper vice is twisting in the vise, then you might not be getting an accurate ft/lb reading off your wrench. Try doing it with a more solid clamp, and maybe a ft/lb wrench instead and you'll probably be ok. Harbor freight has a 1/2" 20-150lb torque wrench for $25 that I've been using for years without a problem. |
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Quoted:
Quoted:
I would get a ft/lbs torque wrench to see where your at on torque when the nut is tight .. under or over torqued can cause problems. Also you might need to lap the uppers face to get the nut to index properly. If I remove material from the face of the upper wount that affect headspacing ? I guess it could if too much was taken off but you only need to remove a couple thousandth of an inch to get it to index properly and I've never had that adversely effect headspace. You could back it off that "smidge" and then rockset it ... but then it's going to be a PITA to remove later. |
| My ruleis min of 50 and I max out a 65 then if I still can not index the gas tube then I polish the face or if its very little like 1/64 to 1/32 then I polish the tooth where its touching....... I have a Lapping tool for the face of the upper and normally only about a 30 second shot will get it over to index correctly.... |
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Anything over 30 ft/lb is ok IMO. I've built/helped-build 3 uppers each in the 35-45 ft/lb range and they've all seen hundreds of rounds without any issues. Sounds good to me. I just got back from the garage. I get right on at 30 lbs. Just over where I need to be at 35 lbs. Then I went to 50, 60, 70 and finally 75 lbs. From 50 up to 75 it was right between the two holes didn't budge at all. If you all think I'm safe with this let me know and I'll take it out and see if it runs...... |
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You're doing it wrong, trying to barrel an upper with a barrel vise. By doing so, you're putting a substantial amount of force on the index pin and the index pin slot in the upper, potentially damaging the upper. You should have a receiver block to barrel uppers.
If you do this with the barrel vise, make sure the front bearing surface of the ring on the barrel as well as the mating surface on the inside of the barrel nut are greased with a thin film of moly grease, this will reduce the torquing force on the barrel. |
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If I recall correctly, in the video on Brownell's website the tech building their sample rifle, state that:
When tightening the barrel nut tighten to 30 ft/lbs. If the gas tube doesn't line up, then increase the to 40 ft/lbs. Don't remember if it was okay to go beyond that or what the max was. But seems to me that anything between 30 to 60 ft/lbs would be okay.... |
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Quoted: You're doing it wrong, trying to barrel an upper with a barrel vise. By doing so, you're putting a substantial amount of force on the index pin and the index pin slot in the upper, potentially damaging the upper. You should have a receiver block to barrel uppers. If you do this with the barrel vise, make sure the front bearing surface of the ring on the barrel as well as the mating surface on the inside of the barrel nut are greased with a thin film of moly grease, this will reduce the torquing force on the barrel. Not saying that the military way is the best way, but the military still uses barrel vises instead of receiver blocks. |
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Quoted:
Sounds good to me. I just got back from the garage. I get right on at 30 lbs. Just over where I need to be at 35 lbs. Then I went to 50, 60, 70 and finally 75 lbs. From 50 up to 75 it was right between the two holes didn't budge at all. If you all think I'm safe with this let me know and I'll take it out and see if it runs...... The bottom of the range is 30 ft lbs not 35 ft lbs. If you're getting alignment at 30+ and you blow through that zone to start looking after 35, sometimes that forces you off the scale (80). Start looking for alignment as you approach 30. It goes without saying, you will need a torque wrench. |
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