03-26-2022, 04:32 AM
If you're using a set screw block, the rear screw hole is opposite the gas hole. Use the screw hole to line the block up over the gas port on the barrel to figure out whether the block should be on the shoulder on the barrel or set just off of it. If it's offset, mark the barrel with the block in the correct position then use the line you drew through the port with the fine tip sharpie to get the block centered. Fine tune with the tube to get as much free play as possible. LRRP's upside down tip sounds good for fine tuning.