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Posted: 11/29/2012 11:31:25 AM EDT
| I have read on here in numerous threads about you don't have to be PERFECT with the tightening of the barrel nut. I don't have a torque wrench so I wasn't going to worry about it too much. When I was tightening the barrel nut though, there's not too much difference between what feels really tight to me, and then loose again. When I've got it pretty tight, the gas tube hole isn't close to being where it needs to be. Then when I loosen it back to line up the gas tube hole, it's loose again, as in I can just spin it with my fingers loose. What have I done wrong here? |
| On rare occasions you may still not get nut alignment at the max of 80 lb/ft of torque. Your options at that point are to try another barrel nut or lightly lap the front of the upper receiver. If you decide to lap the upper only remove about .002". This is just barely through the anodizing. |
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I have read on here in numerous threads about you don't have to be PERFECT with the tightening of the barrel nut. I don't have a torque wrench so I wasn't going to worry about it too much. When I was tightening the barrel nut though, there's not too much difference between what feels really tight to me, and then loose again. When I've got it pretty tight, the gas tube hole isn't close to being where it needs to be. Then when I loosen it back to line up the gas tube hole, it's loose again, as in I can just spin it with my fingers loose. What have I done wrong here? No offense, but new builders with little or no wrenching experience simply don't have a "torque reference" etched into their man hands/arms. If you have worked on vehicles, aircraft, etc you know what various torque values feel like. I would get/rent/borrow a torque wrench and go from there. |
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Quoted:
I have read on here in numerous threads about you don't have to be PERFECT with the tightening of the barrel nut. I don't have a torque wrench so I wasn't going to worry about it too much. When I was tightening the barrel nut though, there's not too much difference between what feels really tight to me, and then loose again. When I've got it pretty tight, the gas tube hole isn't close to being where it needs to be. Then when I loosen it back to line up the gas tube hole, it's loose again, as in I can just spin it with my fingers loose. What have I done wrong here? No offense, but new builders with little or no wrenching experience simply don't have a "torque reference" etched into their man hands/arms. If you have worked on vehicles, aircraft, etc you know what various torque values feel like. I would get/rent/borrow a torque wrench and go from there. No, that's quite alright and kind of what I was getting at. I guess I just don't know if 80 ft. Lbs. is very tight or if I should be jumping on it. Not really, but you get my drift lol |
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I have read on here in numerous threads about you don't have to be PERFECT with the tightening of the barrel nut. I don't have a torque wrench so I wasn't going to worry about it too much. When I was tightening the barrel nut though, there's not too much difference between what feels really tight to me, and then loose again. When I've got it pretty tight, the gas tube hole isn't close to being where it needs to be. Then when I loosen it back to line up the gas tube hole, it's loose again, as in I can just spin it with my fingers loose. What have I done wrong here? No offense, but new builders with little or no wrenching experience simply don't have a "torque reference" etched into their man hands/arms. If you have worked on vehicles, aircraft, etc you know what various torque values feel like. I would get/rent/borrow a torque wrench and go from there. No, that's quite alright and kind of what I was getting at. I guess I just don't know if 80 ft. Lbs. is very tight or if I should be jumping on it. Not really, but you get my drift lol 80 is a lot of torque, IMO. Our 30-80 torque range is liberal. I try to keep it under 50 and lower if possible. |
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While using that type of torque wrench is better than not using one at all, a beam style wrench is preferable because it allows the user to measure the torque being applied in real-time. I've had both styles of torque wrench and prefer the later for installing barrels. The beam style wrench can be had for little money if you shop around. Amazon offers a wide selection but they can be had at your local Auto Zone and the like. |
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While using that type of torque wrench is better than not using one at all, a beam style wrench is preferable because it allows the user to measure the torque being applied in real-time. I've had both styles of torque wrench and prefer the later for installing barrels. The beam style wrench can be had for little money if you shop around. Amazon offers a wide selection but they can be had at your local Auto Zone and the like. I dont have one yet so i cant talk from experience but i think you could always set it at the minimum and once you reach that (clicks) you can reset to to the maximum or 80lbs and continue until you align the gas tube hole and most likely will not reach the 80lbs, thats my idean, once again i dont have experience since im a few months away from beginning my build. |
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Quoted:
While using that type of torque wrench is better than not using one at all, a beam style wrench is preferable because it allows the user to measure the torque being applied in real-time. I've had both styles of torque wrench and prefer the later for installing barrels. The beam style wrench can be had for little money if you shop around. Amazon offers a wide selection but they can be had at your local Auto Zone and the like. I dont have one yet so i cant talk from experience but i think you could always set it at the minimum and once you reach that (clicks) you can reset to to the maximum or 80lbs and continue until you align the gas tube hole and most likely will not reach the 80lbs, thats my idean, once again i dont have experience since im a few months away from beginning my build. That's what a lot of builders do. I've had a couple of REALLY TIGHT barrel nuts, but I've never reached the 80# mark. |
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Quoted:
While using that type of torque wrench is better than not using one at all, a beam style wrench is preferable because it allows the user to measure the torque being applied in real-time. I've had both styles of torque wrench and prefer the later for installing barrels. The beam style wrench can be had for little money if you shop around. Amazon offers a wide selection but they can be had at your local Auto Zone and the like. It is often hard to watch what you're doing AND read the beam wrench indication. There is also no evidence that a beam wrench is more accurate than a click-type wrench, I have the Harbor Freight click-type wrench and it is acceptably accurate (it is easy to check the accuracy if you take a little time - read here for details*). Given the type of measurement you're doing,a click wrench does the job very well. You want AT LEAST 30 ft-lb, so you will torque the nut until a click wrench set to 30 "clicks". (Standard practice calls for tightening to 30 at least 3 times before going on, backing off each time until at least the third.). Once you have at least 30, then you set the wrench for something under your max of 80 ft-lb and continue to tighten until you line up a barrel nut notch with the gas tube hole in the upper. What torque do you wind up with? Something between 30 and 80 ft-lb. There is no need to know what the final torque was. *The procedure requires a bit of explanation. You won't be changing the wrench by "calibrating" it in this way. You will, instead, know what the actual torque at which the wrench clicks is for a given setting. You can do this procedure for a number of different settings, given sufficient weights, which will let you build a table of equivalences. Basically, if you want a particular torque, you check your table and set the wrench for the appropriate click stop based on your actual measurements of how the wrench oerforms. |
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If I were going to mount large numbers of barrels on receivers, I'd buy the proper tool from Brownells to face off the front of the receiver square to its axis. That way you could line up the gas tube holes in the torque sweet spot every time.
I don't have any special tools, just an ordinary 1/2" drive breaker bar, for my two homebuilt uppers, and all their various handguards and barrels. When the sweet spot is not immediately reached, I just keep screwing and unscrewing the nut with reasonable torque, sometimes cleaning off the grease and starting all over again, until I finally get the tube lined up the way I want. Occasionally these have been pretty tight, but anything short of breakage is better than too loose. - CW |
| Here is how I do it. Coat threads with anit seize, torque to approximately 80lbs or what ever it takes on the high side so that everything aligns, mark it, then back it off. Do this two times and then tighten the barrel nut back to that alignment mark. Sometime it takes near 80lbs sometimes it doesn't. |
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