You are comparing apples to oranges. Black Ice is a coating. Nitriding is not a coating, is is a process that physically changes the properties of the steel. As was already pointed out, nitriding can be done to the bore and will not change any dimensions. Any coating can chip, although I'm not saying Black Ice is likely to, but nitride cannot chip and the only way it can wear off is to physically wear away the actual treated steel. I can only speak for CVA quick release breech plugs, but I was told they cannot be nitride treated because they have a sealing rim on the face of the breech plug that relies on actually bending to form fit the mating edge in the barrel and insure a gas tight fit when it is initially installed . Nitriding would make that rim to hard and brittle to bend to a form fit and would it would break. That would not be an issue on other breech plugs that don't have the sealing rim.