Tricks to align gas block?

[usmcspud]

I'm in the process of waiting on my lower and a few other parts and then I can proceed w/ my first AR build.
Is there a "trick" to aligning the FSB w/ the gas port in the bbl?
I am using a free float forearm so there will be no forearm cap to "space" the FSB.
Thanks for any assistance.
Semper-Fi!
Spud

[chuck762]

Some gas blocks will be made to mount up without the handguard cap. Others will require it. Is it held on with set screws or pinned on? More info is needed such as who makes the block.

[usmcspud]

It's an ARMS 41B folding front site. Looks to be a clamp-on. It's still on BO from SWFA.
Thanks.

[chuck762]

You can use a feeler gauge the same thickness cap to space it.
To get it lined up with the hole you can either mark 180 degrees from the gas port and line up the hole that is drilled on all gas blocks for the port or you can lay the upper (flat top) on a flat surface with the sight folded down. The flat surfaces of the receiver and the sight should get it close. There is room to have some misalignment as the port in the block is usually bigger than the port in the barrel. Plus since it is a sight you will need to be able to fine tune the zero. You don't want to have the windage of the rear sight way off.

[usmcspud]

That helps.
Thanks.
Semper-Fi!
Spud

[aplinker]

The 41B comes with a spacer.

[kendog4570]

Handguard caps run approximately .027"

[usmcspud]

That's excellent info. Thanks for your replies.
Spud

[rabagley]

If you don't have a muzzle device on the barrel, you can also plug the chamber with a finger and blow through the muzzle. It's very audible when everything is lined up. You can get a fairly quick feel for where the gas block opening is relative to the barrel opening and also realize how much slop you have (a lot, in most cases).

[usmcspud]

More good info. You folks have helped me immensely.
Thanks again and Semper-Fi!
Spud