AR Barrel chambering methods


Well-Known Member
Mar 12, 2014
I've learned that there are two basic theories for the two points about which a barrel is dialed.
1. Dial in muzzle and breach
2. Dial in neck and lead area, which then requires the muzzle to be clocked

I'm working on an AR 15 barrel blank and want to locate the gas port relative to the lands and grooves.

If I use Method 1, the chamber will be aligned with the muzzle and breach. The gas port would be located by rotating the barrel a fraction of a turn to get the lands and groves lined up. Then extension would then be installed and clocked to the port.

If I use Method 2, the chamber would be clocked to the muzzle which is pointing up. Therefore, the barrel can't be rotated to locate the gas port. The only way to locate the gas port would be to move it up and down the barrel length corresponding with the twist rate and number of lands and groves. This could require several inches of movement which the blank may not have.

Seems Method 1 is the best way to align everything. Just doing my research as I haven't tried Method 1 before.

Looking for some affirmation from others.

J E Custom

Well-Known Member
Jul 29, 2004
I like the Method #1 because it is critical to center the gas port in the grove away from the lands for best performance. To locate the gas port at the right distance from the breach, it should be done before the barrel extension is made up. After the extension is indexed and torqued aligned with the gas port, final head space can be set.

Just the way I do it and others may/can do things other ways. I also do a partial chamber with the barrel extension not installed to keep it clean and free of cuttings and then do the install and finish the chamber and head space with everything in it's proper place.


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