The bore of the SGB is machined to closely fit around .750” diameter mounting bosses found on most M4 Carbines and AR-15 rifles. Nitride coating is considered one of the better exterior finishes for both wear and corrosion resistance. Also referred to as Meloniting and QPQ, or Quench, Polish, Quench finish, or nitrocarburizing, the nitriding process is accomplished by dunking, or quenching the steel in a very hot caustic bath which produces a layer of iron nitride, then polishing the gas block, and re-immersing the gas block back into the hot nitride salt bath. The result produces a finish on the steel which is both extremely hard and wear resistant, as well as extremely corrosion resistant.
This is a stainless steel gas block from Geissele, which has been factory nitrided for the strongest possible resistance to the elements. The Geissele Super Gas Block features two set screws in the bottom of the block, which is perfect for 99.9% of all users, especially when a small drop of red Loctite is added. For those in the 1/10th of 1% whose lives might depend upon a gas block never getting lose, there is a drill hole available to cross-drill the gas block into the barrel.
Charlie's Custom Clones offers the same item in three finishes. Here is the nitride coated, as well as Geissele Stainless Steel Gas Block and the Geissele Black Oxide Gas Block
