After assuring that the weapon is unloaded remove the operating rod spring, guide & operating rod. The spring guide fits into a pin, with spring pressure removed this pin will be free to fall out so beware, don't loose it. Loosen the 4 allen screws holding the gasblock togather, beware there is a small gas tube that fits between the lower gas block & the barrel it'll likely fall out when you seperate the lower block from the barrel don't loose it. The gas pipe is held in the lower block by this tube & should be a loose fit, remove it from the gas block. Now you have the lower & upper gas block halves. Using some emory cloth on a flat surface such as a plate of glass surface the 2 haves where they are held togather by the allen screws until they are flat. When you're satisfied that the 2 surfaces are nice & flat clean the pieces & reassemble. As you tighten the four allen screws use a feeler gauge to assure the 2 halves of the gas block stay parallel. How tight? You be the judge. Restake the screws like the factory did. A note here, the gaspipe that fits into the end of the operating rod should be free to move, it's built that way. I hope I haven't confused you but it's hard to discribe without a drawing.