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Posted: 4/10/2017 12:11:24 AM EDT
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Hey guys,
I've never installed a barrel before. I bought a new barrel with all the necessary parts and I had my go at installing them today. My points of concern are: 1) I tightened the barrel to slightly less than 30 fl/lbs because alignment was too sweet and I didn't want to ruin it with much higher torque. I did the normal tighten x3, but after I went to 30 I backed off just a smidge (less than 1/5 the width of a tooth) to align the gas tube. - Should this be a worry? 2) I got the gas tube in there, but being my first time I am worried I could have bent the tube -- should this be a worry? Image of the tube -- anything to be concerned about with alignment? What will be the symptom when firing if I did it wrong? 
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Needs to be between 30 to 80 lbs, a smidge under 30, could have ramifications sometime down the line. Having a barrel nut come loose is not an experience I would wish upon anybody, you should be able to get it to the next notch with no problem at all.
You did use some type of grease on it didn't you? |
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Quoted:
Not sure the bbl nut can come loose, the gas tube will prevent it. Somebody correct me if I am wrong. That being said, I would redo it to get within the spec. Rare, I know, but I have come to expect just about anything you can think of with some types of guns. |
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Quoted:
I saw one that the nut was loose enough to wear the gas tube allowing gas escape. it was just that little bit that allowed the vibrations to work against the gas tube. Rare, I know, but I have come to expect just about anything you can think of with some types of guns. |
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and then there's really thin barrel shims, although when i ordered my sets, they were .003" which still worked. these go between the receiver face and the barrel flange. not between the barrel flange and barrel nut.
you cut a slit in them to get it past the locator pin, and position the cut behind the locator pin. Bison Armory AR-15 barrel nut shims and another alternative is to take a few spins with a lapping tool on the receiver face, knock off a thousandth or so. arfcom discussion on AR15 lapping tool |
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I have a gun with a Centurion barrel and a milspec barrel nut. Most accurate chrome lined gun I have. It is tightened to 90lbs or a little more. You do not have to limit yourself to 3 times and tighten. That is the spec'd way. If you tighten and back off multiple times you can get your torque value down some. I do not recommend just cranking it down to 90lbs but my point is 30-80 is a wide range. Moreover if you do it incrementally and easy you shouldn't be screwing anything up with values slightly north of 80.
Again this gun is capable of MOA groups with federal gold medal match. I would tighten it as opposed to leaving it at 28-29 lbs. I would also do several hand tighten and back offs to distribute the grease more evenly before I started gently ramping up my torque. Your gun your choice. YMMV. *and no do not loosen to align or get a torque spec, always end by tightening. |
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