RE; case coloring vs case hardening. Case hardening is done by heating a piece of low carbon steel to a temp above it's critical temp in a carbon rich mixture which causes the metal to absorb carbon into it's surface. Depth depends upon both temp & time. It is then quenched in water while still above the critical temp which causes hardening of the carbon rich surface "case" to take place. The colors are a by-product of the process from oxidation of the surface & when done with intent to produce the colors is often referred to as "Color Hardening". Loss of color does not indicate loss of hardness as the case is much deeper than the colors.
I believe, but not totally sure, the colors can be formed with the temp a little below the critical temp. This greatly lessens the possibility of warpage, shrinkage etc, "BUT" however leaves the steel in a near annealed condition. I firmly believe the makers put that hard case on there for a definate purpose. Personally, I would never have a frame annealed without re-hardening it. Either have a professional who knows about heat treating do the proper Color-Case Hardening, or forget it. The other acceptable process is the one I have posted about which I call "Pseudo Case Coloring". This is done using cold blue streaked on with part at about 160°F. while not producing as good a color as desirable for a high grade gun, it is perfectly safe.
