https://midstatefirearms.com/product/cheap-ass-750-steel-set-screw-ar15-barrel-dimpling-jig/

shipping available

Want to dimple your ar15 barrel 180 degrees from the gas port but don’t want to waste money on a tool that costs a bunch of money? Use this AR-15 barrel dimpling jig instead! This no-frills AR-15 barrel dimpling jig will help you figure out where to drill that dimple for your gas block set screw if you’ve got a barrel with no dimple.  

It’s just a wonky gas block with a hole drilled from the gas port through the top.  

Step 1: slide it on the barrel.

Step 2: look through the top and center it on the gas port.

step 3: tighten the hex screw to hold it in place 

step 4. drill a shallow dimple in the barrel through the open set screw hole. 

Simple as that!  You only need one dimple, 180 degrees from the gas port, and it should work with any gas block.  Virtually all set screw gas blocks have a set screw that is 180 degrees from the gas port. 

note: you could maybe use this as an actual gas block, too.. but we wouldn’t necessarily recommend it.