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5/14/2017 5:07:53 PM EDT
Have all parts and tools for upper with FF hand guard over low pro GB.

Is this order correct?

Pin gas tube to block

Insert barrel into upper receiver
Slide gas tube assembly on and set with set screw
Tighten barrel nut and torque
Install flash hider
Install handguard

Is this the proper order?
5/14/2017 5:16:42 PM EDT
[#1]
Install the barrel nut before sliding on the gas block
5/14/2017 5:18:43 PM EDT
[#2]
Tighten the barrel nut first.

The gas tube has to pass through the scallops on the barrel nut.

There are lots of videos on the interwebz, do a search.
5/14/2017 6:37:43 PM EDT
[#3]
Here's the proper steps.

- Support upper with proper tools (receiver block, BEV block, etc) in bench vise.
- Insert barrel into upper, slide on barrel nut, grease threads and then hand tighten barrel nut.
- Using torque wrench, tighten and loosen to proper torque spec a few times.  Do final torque and ensure cutouts in barrel nut align with gas tube hole in upper receiver (not necessary with some barrel nuts).
- Install gas tube in block, then slide block onto barrel, align properly, and tighten set screws (preferably with some form of threadlocker).
- Support barrel with proper tools (reaction rod, barrel blocks, etc) in bench vise and install muzzle device.
- Slide handguard over barrel and properly secure it to the barrel nut.

You're done.
5/14/2017 6:53:08 PM EDT
[#4]
Thanks guys. I assembled an upper years ago but haven't done it in awhile. Just wanted to make sure.
5/15/2017 9:44:17 AM EDT
[#5]
If you're starting with a stripped upper, it's easier to install the dust cover first.
5/16/2017 5:51:17 AM EDT
[#6]
Check your individual parts, though. I have one hand guard that has to be installed before the gas tube, because of the design of it. It has the groove under the rail for the gas tube, but threads onto the barrel nut to mount the handguard. To say that doing a low-pro, hidden block under one of those can be a challenge is a bit of an understatement.
5/16/2017 10:37:46 AM EDT
[#7]
Quote History
Quoted:
If you're starting with a stripped upper, it's easier to install the dust cover first.
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And it helps fill the void up in the clamshell block if you are using that.  Not sure how much support it could provide (the pin might I guess) but it is a big hole with a thin little web across the bottom otherwise.

I always do the dust cover and forward assist before I do the barrel.  Every gun I have the barrel nut and/or handguard holds the dustcover pin in place too...
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