The setting that you settle on will depend on how the rest of your build out goes, and what type of ammo you are going to use, and how you want the gun to feel. the easiest way to figure it out is once the build is finished, get whatever ammo you will use in it most often, start on the highest gas setting (farthest to the left, facing the muzzle) and shoot, adjust the gas down, and shoot again. repeat until the gun stops cycling, and then go back up to the last spot. this process really wont be completely accurate until the weapon is broken in. you can either wait for about 200-500 rds, or do an initial adjustment, and then do another at 500 rds. it may not make a difference. but the rifles action will change after a break-in, which can affect cycling.