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4/11/2008 3:09:36 PM EDT
Does anyone know a good trick for aligning the gas holes in the barrel and gas block.  New 10.5 upper that is not cycling.  The holes where out of alignemnt so preseure was low.  thanks for your assistance.
4/11/2008 3:13:37 PM EDT
[#1]
Paperclip or welding wire of appropriate diameter bent 90 degrees, inserted in the barrel through the FSB gas port.
4/11/2008 5:40:00 PM EDT
[#2]
I just purchased a JP gas block, and the instructions say to blow compressed air through the front of the barrel and listen to the sound of the gas coming out of the block to help align the holes.
4/11/2008 7:01:21 PM EDT
[#3]
You should also be able to measure it pretty darn close with a decent pocket scale (ruler) or using the depth gauge on a caliper.

Once you have measured the location of the port in your gas block, from either the front or rear, you can measure the same distance from the port on your barrel and make a mark with a pencil or sharpie.  I recommend measuring to the center of the gas port for the max tolerance leeway...

if you have the shoulder on your barrel, you can usually just space the gas block one handguard cap-thickness from the shoulder, if your gas block has the same port position in relation to its rear face as a standard FSB.
4/12/2008 11:48:46 AM EDT
[#4]
If the front sight base is pinned to the barrel then you're out of luck on changing the alignment and will need to send it back.

If it's a set screw gas block then you should be able to get it aligned by leaving a small gap between the rear of the gas block and the shoulder on the barrel, gap should be about the thickness of two playing cards.  Left/right alignment should be easy enough to eye-ball.

The hole in the bottom of the gas block is made much larger than the hole in the barrel in order to make it easy to align and prevent the type of problem you are reporting.
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