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dfletcher
09-27-2008, 7:18 PM
Aside from snugging up against the barrel shoulder and lining the tube up through the barrel ring, are there any little tricks to ensure the gas port in the gas block is lined up with the gas port in the barrel?

Also, I bought a clamp on type GB (.750 ID) and the darn thing kept walking forward when I was at the range today. I have a 7.62X39 barrel, a little more recoil, but I think the thing should stay in place. I see 3 basic styles of securing the after market gas blocks - a clamp on (clam shell) type with horizontal screws, a clamp on with 2 separate straps running under the barrel and a set screw type.

Are there any after market GBs that use taper pins? I'm kind of liking the idea of a piece of solid steel securing everything in place.

ar15barrels
09-28-2008, 1:16 AM
The biggest improvement is to drill a detent in the barrel, or a cross pin.

http://ar15barrels.com/tech/detent.jpg

Almost any gas block can be pinned like this:
http://ar15barrels.com/tech/pri-pinned.jpg

ar15barrels
09-28-2008, 5:22 PM
Aside from snugging up against the barrel shoulder and lining the tube up through the barrel ring, are there any little tricks to ensure the gas port in the gas block is lined up with the gas port in the barrel?

You don't usually slide the gas block all the way back.
You usually leave room for a handguard cap.
Some barrels and some gas blocks account for the lack of a handguard cap though.

m24armorer
09-28-2008, 5:27 PM
Gee, did everyone just not notice that almost all gas blocks have a hole on the underside. If you are removing your original sight base, knock out the sling pin and mark the thru hole.

Then install your new block or base and align it's bottom hole with your marking.

Works for me, well, most of the time.

dfletcher
09-28-2008, 5:50 PM
You don't usually slide the gas block all the way back.
You usually leave room for a handguard cap.
Some barrels and some gas blocks account for the lack of a handguard cap though.

I should have noted the handguard cap, leaving it in place, which I did. I think I'll pin the GB in place after I ensure everything's lined up.

What do most do step by step - mount the GB, then add the tube & pin once the block is on the barrel? Or do you attach the tube 1st, then mount the whole thing? Make a difference?

ar15barrels
09-28-2008, 6:03 PM
Gee, did everyone just not notice that almost all gas blocks have a hole on the underside.

Not almost all, ALL of them do.
Had to drill the hole in the gas block for the gas to get the the gas tube somehow.

I tell people to make a pencil mark half way around the barrel from the gas port.
Then look through that bottom hole to be sure they are good front-back.
Tighten the front setcrew, then install and tighten the rear setscrew.

ar15barrels
09-28-2008, 6:05 PM
What do most do step by step - mount the GB, then add the tube & pin once the block is on the barrel? Or do you attach the tube 1st, then mount the whole thing?

If the gas block is to be installed on the barrel, I put the gas tube into it first.
This lets me fine adjust the gas tube up/down as I go to slide it into the reciever.
I like to make sure they go in nicely, without a bias in any direction.