Kutters instructions are pretty accurate, from the links burying a piece in charcoal for 3 hours does nothing really.
The old-school Purdey way to charcoal blue was to pull the piece from the coals and burnish periodically with tow (loose flax/canvas material) and lime. This would produce a uniform and deep-gloss black.
Joe Wood - If you are going to hot blue that guard I suggest you anneal it first. The original charcoal blue would have hardened that piece and you can end up with a plum brown/red colour when initially using the hot salts method.
