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Posted: 3/11/2012 9:04:34 PM EDT
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So I'm having a bit of a problem. Doing an upper build and I'm having trouble getting the gas tube to line up with the holes. As I put the barrel nut on it screws on clean and then you begin to feel pressure. Once pressure begins the nut turns very little before its way too tight to tighten anymore, it will turn under pressure from a wrench maybe a quarter of a turn. I've used a torque wrench on it at 90lbs and it won't go any tighter. No biggie I thought, but the gas tube doesn't want to line up exactly. I can get it to fit but it puts some torque on the gas tube which I'm not comfortable with. I finally got the gas system to work but that bend makes me nervous. I'm sure that the nut isn't cross threaded but I can't get it to go tighter. I'm worried if I loosen it to catch the next hole in the nut its not going to be tight enough...
Any advice here? Thanks in advance, zac. |
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Quoted:
So I'm having a bit of a problem. Doing an upper build and I'm having trouble getting the gas tube to line up with the holes. As I put the barrel nut on it screws on clean and then you begin to feel pressure. Once pressure begins the nut turns very little before its way too tight to tighten anymore, it will turn under pressure from a wrench maybe a quarter of a turn. I've used a torque wrench on it at 90lbs and it won't go any tighter. No biggie I thought, but the gas tube doesn't want to line up exactly. I can get it to fit but it puts some torque on the gas tube which I'm not comfortable with. I finally got the gas system to work but that bend makes me nervous. I'm sure that the nut isn't cross threaded but I can't get it to go tighter. I'm worried if I loosen it to catch the next hole in the nut its not going to be tight enough... Any advice here? Thanks in advance, zac. you went to 90ft/lb???? your supposed to hit 35ft/lbs, then torque to the next hole. 85ft/lb is the max |
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Quoted:
So I'm having a bit of a problem. Doing an upper build and I'm having trouble getting the gas tube to line up with the holes. As I put the barrel nut on it screws on clean and then you begin to feel pressure. Once pressure begins the nut turns very little before its way too tight to tighten anymore, it will turn under pressure from a wrench maybe a quarter of a turn. I've used a torque wrench on it at 90lbs and it won't go any tighter. No biggie I thought, but the gas tube doesn't want to line up exactly. I can get it to fit but it puts some torque on the gas tube which I'm not comfortable with. I finally got the gas system to work but that bend makes me nervous. I'm sure that the nut isn't cross threaded but I can't get it to go tighter. I'm worried if I loosen it to catch the next hole in the nut its not going to be tight enough... Any advice here? Thanks in advance, zac. So you basically don't know what you're doing. If you had read up on this process you would know that the torque range for the M16/M4/AR15 barrel nut is 30 ft lbs to 80 ft lbs 1. Grease the threads with approved grease (Aero Shell 33 MS) or similar 2. Arrange weld spring and snap ring so that they are open on top 3. Look for alignment as you approach 30 ft lbs You blew through your prime alignment which may have been around 35 or 40 and now you are beyond the range trying to find the next alignment. Not good. My advice to you is to get a different, unused barrel nut and try it again the way I just described. The gas tube needs to free float its way into the receiver without the barrel nut pushing on it. Good luck. |
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Quoted:
This. Except... My advice to you is to get a different, unused barrel nut and try it again the way I just described.
The aluminum threads on the receiver are what get distorted, not the steel barrel nut. Although a different nut will come to a different alignment most likely, so swapping them out can move your gas tube slot alignment around. If you have extra barrel nuts its easy to swap a couple until you get an easier alignment. |
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Quoted:
Except... My advice to you is to get a different, unused barrel nut and try it again the way I just described.
The aluminum threads on the receiver are what get distorted, not the steel barrel nut. We all (who wrench) know that. At 90 ft lbs plan on some thread deformation at the receiver. What's done is done. Steel always wins. That why proper procedure is so important at the barrel nut. It is likely that a new barrel nut will present its notches at a different location and hopefully a favorable location for the OP. The reason for this is that the barrel nut (#2) threads likely will not have been cut with the same relationship with the notches. We're hoping that the difference will be favorable to the OP and allow alignment with reasonable torque. The other option is to take some material off the receiver face, but that's AR Building 201. We need to get through 101 first. |
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Well from reading it looks like I got some bad information in the book I bought on the subject. Not surprising considering the quality of the book. Should have known better. I'll pull it apart and take a look at everything and make sure that I didn't damage something. Excellent advice guys, and thanks for the help.
Zac. |
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Zac, look at the build it yourself section, there is a tacked thread that has instructions to do pretty much anything.
To save you some time, here it is hot linked http://www.ar15.com/forums/t_3_4/226782_Assemble_your_own_LOWER__UPPER__FREE_FLOAT__TRIGGER__GAS_BLOCK___Step_by_step_instructions_.html |
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http://www.brownells.com/.aspx/lid=11004/learn/
They decided to market this one so in the free You Tube files watch for AR MPR and Gavin Toobe I think all the parts are still there..... http://www.youtube.com/watch?v=0J57W4xz6Uw |
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Using the help section in the website I think would have been the best idea. In the past I've gotten burned on learning to do stuff with internet related stuff and have had better luck with books. Looks like this was not one of those cases. Thanks for the link guys, I'll definetely take a look at them and learn from my mistakes.
Thanks zac. |
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