Recently bought Faxon 556 barrel that did not come with gas block dimple. Rather than free hand made a jig from an old adjustable gas block that did not ever adjust well. Simple 5/32 bit and drill press/vice. Drill from threaded hole thru the block. Then use threaded hole to line up on gas port. If you want to go crazy put a point on a set screw to lock in the hole I used the standard screw with perfect result. I was surprised to find the gas block steel much harder than the barrel. Since doing this I found a site online that actually sells a gas block pre-drilled for this with the additional statement "and you can still use it as a gas block"