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Posted: 2/28/2006 5:26:55 PM EDT
I have built a few uppers and lowers and they all go together fine.. My biggest problem is after the gastube is installed I install the bolt and carrier and the gas tube rubs on the carrier where it goes in..

Then I have to use a long dowel or old cleaning rod to mess with it untill I figure out how it needs to be bent to make the carrier slide right in.

My question is.. Is there an easier way to do this or is it just trial and error?
Thanks
Link Posted: 2/28/2006 5:45:27 PM EDT
I needs to know too.
Link Posted: 2/28/2006 5:57:01 PM EDT
I use a piece of gas tube about 4 inches long when I am indexing the barrel nut and delta ring assembly, placed inthe delta ring hole, with the vise holding the barrel pointing up. When everything is algned properly the gas tube piece will fall into the receiver. It is then properly in place. I then remmove everything from the vise and insert the proper gas tube , pin it and put on the handgurds and slide in the BCH and we are ready to go. A proper size dowel or even the right size screwdriver shank would also work. You do not ever want to bend the gas tube. Thansk for the opportunity to share something I learned along the Black Rifle Way. ET
Link Posted: 3/1/2006 4:09:05 AM EDT
i eye ball it and bump the bbl. nut if needed.
Link Posted: 3/1/2006 5:27:52 AM EDT
It can be aligned by eye if all you want to do is make the rifle function, but a bit more care is needed if you want to do it right. If the gas tube drags on one side, it will wear and eventually pass enough gas that a FTF will result (and it will be merry hell to find your first time). Install the gas block (lightly, so you can remove it easily) and gas tube with the handguards and/or free float tube off, then watch the tube as you slide the bolt carrier group home; if the tube moves, remove the gas block and lightly bend the gas tube in the direction it needs to go. Repeat the process until the gas tube doesn't move when the carrier is inserted. This will minimize wear over the life of the barrel, and even allow you to reuse the gas tube with several barrels; check the diameter of the "mushroom" at the end of the tube - if it's full diameter you can reuse the tube with no problems.
Link Posted: 3/1/2006 9:23:26 AM EDT
I’ve always spent the extra time to align it perfectly. I’ve read that bending the tube is a bad idea in that it’s likely to spring back after repeated heating.

A great deal of building and AR is very simple but there are a couple fine points that need slow methodical attention. Gas tube alignment is one in my book. Anyone can do the easy stuff. You start to be a better builder when you realize when you need to be very careful.

When I can’t get to sleep I build and AR in my head. I guess I’ve built hundreds that way. I normally nod off before I’ve got it built but the practice has revealed answers to many of the “problems” I encountered along the way.

Did that sound a little too Zen?

Maybe I’m cracking up.
Link Posted: 3/1/2006 2:39:13 PM EDT
[Last Edit: 3/1/2006 2:40:32 PM EDT by M4Madness]

Originally Posted By ET1814:
I use a piece of gas tube about 4 inches long when I am indexing the barrel nut and delta ring assembly, placed inthe delta ring hole, with the vise holding the barrel pointing up. When everything is algned properly the gas tube piece will fall into the receiver.



I do something similar:

The first thing I do after torquing the barrel nut to 30# is look at the cloverleaf gas tube hole in the front of the receiver from INSIDE the receiver. I then tighten more if needed until I can see that there is no high point of the barrel nut blocking it. Then I insert a full-length gas tube from the INSIDE of the receiver through the delta ring assembly and barrel nut. I insert it as far as possible then look straight down on the barrel to see if the gas tube is perfectly centered over the barrel. I then tighten the barrel nut as necessary to get it straight.

Another thing you can do is put a short section of gas tube into the bolt carrier key and attempt to slide it forward in the upper receiver. When this short section of gas tube will clear the barrel nut without touching, you're done.
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