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10/15/2015 7:13:19 PM EDT
is there a specific gap between gas block and the lip behind the gas block?
10/15/2015 7:53:24 PM EDT
[#1]
Quoted:
is there a specific gap between gas block and the lip behind the gas block?
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For most gas blocks, the port is positioned to accommodate a handguard cap between the block and the barrel's shoulder behind the gas port.  A handguard cap is something like 0.025" thick, so there is a "specific" gap, but it gets sort of complicated with some barrels and some blocks.  Almost all gas blocks have a larger opening than the barrel's gas port so alignment isn't quite as critical, but it's always better to get it lined up as closely as possible.

There's a way to find the exact spacing you need with your barrel if your gas block uses setscrews, since the rear setscrew will line up perfectly with the block's port.  Take the rear setscrew out, put the block on the barrel and turn it bottom-up.  Line up the empty setscrew hole with the barrel's gas port and see how far forward of the shoulder the block sits.  That's the specific gap you need for that barrel and that gas block.
10/15/2015 9:13:08 PM EDT
[#2]
hey, thanks for the reply, very good method
10/16/2015 1:43:26 AM EDT
[#3]
GHP pointed out a good way to determine any gap. Just from my experience, the low profile GBs are designed to be pushed up against the shoulder on the barrel, but you never can be too sure...
10/18/2015 1:19:13 PM EDT
[#4]
I use shim washers meant to replace the cap.
A quick measurement will tell if the block needs to be spaced out from the shoulder.
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