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Posted: 10/19/2014 9:35:18 AM EDT
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I torqued to 80lbs and the alignment for the gas rod was a hair off. So I tightened a little more and snapped a piece of a tit on the barrel nut. I know I over tightened. Is it ok to leave the barrel this way or should I back off to lower lbs. of torque? Should I replace the barrel nut which means I need to disassemble everything. Windham Barrel and PSA blemished upper . Did I F up my barrel at all and my upper with the exception of the obvious.
I'm pissed at myself Thanks edit:spelling |
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Take a round in your hand and run the nose tip of the bullet over the feed ramps on the barrel and receiver. You are feeling for if the barrel feed ramps are extending past the receiver, the nose of the bullet will snag.
Not the clearest pic but here I am sliding a bullet into the chamber by hand feeling for snags: 
Sometimes when building a AR with different manufactures example Colt lower and a LMT barrel, even proper torqued barrels will lead to some gap in the feed ramps, so I do this to test for that too, if I find a rough spot I Dremel it smooth ( I know many will poo poo cutting on guns) but it works. You can also purchase headspace gauges from Brownells that will tell you if you are too loose or tight. Unless you are too lose not really needed and if you went to 80lbs you are not too loose. Hope this helps |
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I would think that if you messed up a tooth on the barrel nut, it wouldn't really matter as long as the gas tube is properly aligned with the hole through the upper and the bolt carrier key now slides freely over the gas tube without much resistance.
I've done the same thing using a pin type wrench. I don't think you hurt the barrel or the upper. |
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I know on the Mk18 CQB upper with DD forearm barrel nut is torqued between 50-60 lbs. I remember FH are torqued between 20-30 lbs. For a standard type barrel I'm thinking the barrel nut is also torqued 20-30 lbs. My electronic copy of the Techincal Repair Standard for the M4A1 can't find the torque specs but I know its in the current hard copy at the office (just did a Mk 18 UBR last night)
CD |
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Quoted:
I know on the Mk18 CQB upper with DD forearm barrel nut is torqued between 50-60 lbs. I remember FH are torqued between 20-30 lbs. For a standard type barrel I'm thinking the barrel nut is also torqued 20-30 lbs. My electronic copy of the Techincal Repair Standard for the M4A1 can't find the torque specs but I know its in the current hard copy at the office (just did a Mk 18 UBR last night) CD IIRC a standard barrel nut should be tightened 3x at 30 lbs to bed the threads, then you can go as high as 80 lbs to align the nut for the gas tube. It is stated to NOT exceed 80 lbs. I've gone as far as 70 lbs before but even that makes me a little nervous. That's also the same thing we did at a manufacturer I worked for. |
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Quoted:
Take a round in your hand and run the nose tip of the bullet over the feed ramps on the barrel and receiver. You are feeling for if the barrel feed ramps are extending past the receiver, the nose of the bullet will snag. Not the clearest pic but here I am sliding a bullet into the chamber by hand feeling for snags: http://i83.photobucket.com/albums/j292/stukas87/S6003164_zpsc92e964a.jpg Sometimes when building a AR with different manufactures example Colt lower and a LMT barrel, even proper torqued barrels will lead to some gap in the feed ramps, so I do this to test for that too, if I find a rough spot I Dremel it smooth ( I know many will poo poo cutting on guns) but it works. You can also purchase headspace gauges from Brownells that will tell you if you are too loose or tight. Unless you are too lose not really needed and if you went to 80lbs you are not too loose. Hope this helps Disregard this post, he hasn't a clue what he's talking about. Barrel nut torque will NOT affect feed ramps. Dermel? |
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Quoted:
Disregard this post, he hasn't a clue what he's talking about. Barrel nut torque will NOT affect feed ramps. Dermel? Quoted:
Quoted:
Take a round in your hand and run the nose tip of the bullet over the feed ramps on the barrel and receiver. You are feeling for if the barrel feed ramps are extending past the receiver, the nose of the bullet will snag. Not the clearest pic but here I am sliding a bullet into the chamber by hand feeling for snags: http://i83.photobucket.com/albums/j292/stukas87/S6003164_zpsc92e964a.jpg Sometimes when building a AR with different manufactures example Colt lower and a LMT barrel, even proper torqued barrels will lead to some gap in the feed ramps, so I do this to test for that too, if I find a rough spot I Dremel it smooth ( I know many will poo poo cutting on guns) but it works. You can also purchase headspace gauges from Brownells that will tell you if you are too loose or tight. Unless you are too lose not really needed and if you went to 80lbs you are not too loose. Hope this helps Disregard this post, he hasn't a clue what he's talking about. Barrel nut torque will NOT affect feed ramps. Dermel? So what is your advice Avidrook? So you are saying feed ramps always line up with no gaps? Is it possible he tightened the barrel feed ramps past the receiver unlikely, but just ensure the ramps are good to go is this not a valid method to check. Also if you have feed ramp issues then you would not polish them? Guess what send a rifle back to a manufacturer guess what some do use to polish feed ramps... a Dremel. How about offering something beside saying someone has no clue? As always the veil of the internet is easy to hide behind. |
| if its tight and feed ramps are lined up correctly, you may not want to remove it. This happened to me recently and I sent it to ADCO. They told me to leave it because if they took it off, more than likely the upper threads and the barrel nut would be stripped. Mine was so tight I could not remove it. If yours comes off easily, maybe you should try. |
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When torqueing a barrel nut are you using a math formula or calculator to take in consideration of the length of the tool your hooking up to your torque wrench?
If you not using a socket on a torque wrench any extra positive length from the wrench to the fastener is added torque to the fastener. Something like this for a straight extension. https://www.motorcraftservice.com/renderers/torquewrench/wrench_formula_en.asp?type=180degstraight Here is a whole page of different toque wrench add on calculations https://www.motorcraftservice.com/renderers/torquewrench/wrench_formula_main_EN.asp If you have your wrench set to 90 deg and its isn't over 2 inches long you don't need a conversion calculation. |
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Quoted:
IIRC a standard barrel nut should be tightened 3x at 30 lbs to bed the threads, then you can go as high as 80 lbs to align the nut for the gas tube. It is stated to NOT exceed 80 lbs. I've gone as far as 70 lbs before but even that makes me a little nervous. That's also the same thing we did at a manufacturer I worked for. Quoted:
Quoted:
I know on the Mk18 CQB upper with DD forearm barrel nut is torqued between 50-60 lbs. I remember FH are torqued between 20-30 lbs. For a standard type barrel I'm thinking the barrel nut is also torqued 20-30 lbs. My electronic copy of the Techincal Repair Standard for the M4A1 can't find the torque specs but I know its in the current hard copy at the office (just did a Mk 18 UBR last night) CD IIRC a standard barrel nut should be tightened 3x at 30 lbs to bed the threads, then you can go as high as 80 lbs to align the nut for the gas tube. It is stated to NOT exceed 80 lbs. I've gone as far as 70 lbs before but even that makes me a little nervous. That's also the same thing we did at a manufacturer I worked for. Check the TRS last night and that's the procedure. CD |
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1st, I am not a gunsmith. BUT, I have put together more than a few AR's for myself.
I first do a visual check to make sure everything looks ok. Over the years I have found a few things that didn't look correct and sent parts back for exchange. (Vendors are more likely to exchange if it has not been installed.) I always use a torque wrench. (Every time.) I clean the threads with a good tooth brush, Lube all the threads (inside and out) and torque to around 30-35 #'s. I take it apart, clean it again, lube it again and torque to 35-40 #'s. I then take it apart again, clean the threads, lube it again and torque to 40 to 45 #'s, (checking for the gas tube placement, adjust as needed.) I have never had one come loose, broke anything, or anything move. I got this information here several years ago ( lots of knowledge here) and followed it and it works for me. If you over torque you take the chance of breaking things. I go slow, watch/feel how it is going together. If something doesn't feel right, I stop take it apart and check it again the best I can. A very few times I have found very tiny pieces of metal I missed the first time or a metal burr. Just clean it up and start over. Yes! I know that each of us may do it their own way and may have a good reason. So just pick what may work for you and try it. Good luck! Ron |
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I don't see what purpose "looking at the feed ramps to see if they're lined up" would serve, except maybe to suggest that the alignment pin in the barrel had snapped off. Which, by the way, is not very likely in any case and certainly not likely due to nudging a barrel nut just past 80 foot/pounds.
OP, the real procedure IS to torque to 30 foot/pounds three times, then on the fourth go tighten past 30 foot/pounds to align the first available barrel nut notch. If you can't get one to line up on the fourth go, back off and try again. Breaking a tit off of a barrel nut is usually not because of torque, but because the wrench isn't holding the nut firmly enough. This is especially true when removing the nut, but it applies in both directions. Also, the barrel nut torque value is dependent on the kind of grease used on the threads. The TM's 30-80 foot/pound spec is based on using a MIL-G 21164 compliant grease like Aeroshell 33MS. If you used no grease, or something else, the torque you see when tightening the nut isn't going to relate to the conditions expected in the procedure. In other words, that 30-80 foot/pounds is really only valid if you used the right grease. It's not hard to find, and it's not expensive, but some people insist on using the absolutely cheapest (and least expensive) grease they can lay hands on to use in assembling the parts they've spent many hundreds of dollars to buy...I just don't get that part at all. |
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