Best design i have found - Faxon Firearms Adjustable 3 Screw Low Profile Gas Block

I have 5 of these on different uppers. One on .458 about 600 rounds. One on .556 proof carbon barrel with around 6000 rounds. Best advice is buy this and put neverseize on the threads. Hold the denting back and run the screw all the way out, grease, put it back in. Setting 18 plus is in the mode that puts the excess gas outside of the carrier. It will last forever like this. All the other brands seize around 5000 give or take and are not as serviceable.