Thanks 454fan. There is no slot on this gas block, The allen screws don't clamp the block together, they screw in to the barrel. I took a micrometer to the barrel and it's .750 exactly as it should be. The inside of the gas block however is .734 or so. I'm gonna have to use some sandpaper or something and hone it out a bit. For now, I found a different gas block that will work.