We do NOT install FSBs on any surface coated/hardened barrel.

* Nitro carburized interior and exterior finish which is also applied to the barrel extension and gas port during heat treating and creates a monolithic black finish that is superior to hard chrome. The process does not add material to the internal dimension of the bore, increasing surface hardness to between 58-65 HRC, lowering bore friction, enhancing surface lubricity, improving running wear performance, enhancing corrosion resistance and heat resistance over industrial hard chrome.

In addition, the barrel extension and gas port are also surface converted minimizing barrel extension wear, increasing corrosion resistance and limiting gas port erosion.