Ed, how can you say you are using low heat when your bringing out temper colors that indicate ranges of 500-600 degrees? The millions of double's that were given the bone and charcoal treatment stand as pretty good evidence that the process is not unsuitable when properly done. I routinely have my students do bone and charcoal color case hardening on parts for steam engines I have them build in my manufacturing class and the process is not that difficult. However, if any of them turned in work that looked like some of the guns pictured, I would fail them without a second thought.