AR15 barrel mounting
How does one correctly position a barrel to an upper while torquing the barrel nut so that the barrel is inline & true to the upper? I understand the barrel insertion to the upper but when the nut is tightened barrels appear to go slightly left of the upper's center. Is this a result of an over spec upper? Or how tight does the nut need to be? 30-50 ft lbs?
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Well the barrel has a pin and the receiver has a notch as you know. As far as the barrel turning inside the upper it is so small a minute fraction that this doesn't matter. There's no way in the world of preventing this movement if any. The problem is more in regards to getting the gas tube to line up perfectly and still be able to torque the barrel nut sufficiently. I've had barrels that I removed that were torqued to over 100 lbs. I've personally tried removing a barrel on a DPMS lower with a magazine block that blew the side of the magazine well out that when I removed it the torque wrench read 124 lbs. I've had some that were torqued to 20. Ideally the 30-50 lbs. is correct but try getting there.
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quote:Originally posted by armilite1015
I've personally tried removing a barrel on a DPMS lower with a magazine block that blew the side of the magazine well out that when I removed it the torque wrench read 124 lbs.
Wow that hurts.
I am sure you are aware that the mag blocks are not meant for barrel removal/installation. Sounds like a you needed a receiver block for that job [B)]0 -
quote:Nwcid
Advanced Member
USA
8098 Posts
Posted - 09/15/2010 : 12:45:48 AM Show Profile Email Poster Reply with Quote
quote:Originally posted by armilite1015
I've personally tried removing a barrel on a DPMS lower with a magazine block that blew the side of the magazine well out that when I removed it the torque wrench read 124 lbs.
Wow that hurts.
I am sure you are aware that the mag blocks are not meant for barrel removal/installation. Sounds like a you needed a receiver block for that job
That did, and I had a set but you think I could have found them at the time. Then shortly after this happened wouldn't you know it there they were.0 -
NEVER, NEVER NEVER NEVER, NEVER, ever do this when removing or installing a barrel.., reciever blocks are made for barrel installation/removal. 0 -
That really sucks, BUMMER! 0 -
If misalignment is a problem with the particular barrel/receiver combination, a dowel inserted through the front sight base can be used to apply torque in the opposite direction as the nut is tightened. 0 -
We torque the nut to a minimum of 30 ft/lbs and then continue til the gas tube is lined up. Max torque per the Army TM is 80 lbs.
In the ten years I have been doing this job (probably 1000 or so barrel changes) I have only had a few that could not be aligned using this guidance.
I have to assume that Colt had some input into the TM specs and put some thought/engineering into it.0 -
Thank you all for the comments but be advised a tread will resist stretching when torque is first applied. When a thread has been torqued for a period of time it'll relax & stretch so it's a great idea to apply counter pressure to attempt straightness but it'll never stay there due to the torsional effects of battery trauma, heating up & cooling down, & thread strength torsional evenness. Also being Chromed may vary the alignment. Armilite1015 I feel that you have one of the best upper receivers on that gun as it appears to be a YankeeHill. It's only my personal opinion that I would select DPMS if no other manufacturer was available for whatever part I needed. Thank you all. Armilite1015 who makes that hand-guard on the top picture of those 3 displayed? (sorry I don't mean to change the topic) 0 -
If you are referring to the top picture in my signature post you can not buy that hand guard for any price. That is an original Portuguese/Nato/Transitional model AR10 1950's era. Not even in the same ball park as the current AR10's.
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