Hello everyone! I am currently building my first custom AR15. I purchased a Ruger 5.56 NATO barrel from a guy in one of the AR Groups I belong to and it has what look like pin holes where the gas block mounts. The holes are on the top of the barrel near the exhaust "hole". I am assuming this means the block I choose must be fixed to the barrel using those pin holes. Since I am unfamiliar with this type of gas block mounting I wanted to ask if anyone knows where i can get a gas block that will fit this barrel? In all my searches I am only locating gas blocks that mount with the set screws. HELP!