So after 1964 through I think 1973 Winchester went to an investment cast “graphitic steel” receiver. Made the same way rugers are made but with an alloy. I know tigers can be case hardened and the real question is the content of the steel.
I know this metal does not take to a hot blue, it does however take to a rust blue. Do you think it can be color case hardened?
Those gorgeous swirling colors of old case hardening were not from intention but as a by-product of case hardening plain carbon steel using particular techniques. Chapel or perhaps Howe of the old gunsmith manuals has an extensive section on case hardening of carbon steel, bluings of different sorts, etc. Some of the old formulas though are effectively banned using such things as cyanide and mercuric compounds.
More modern alloys are generally stained with some sort of secret sauce to recreate the resemblance to case hardening (similar to cold bluing) which requires a bit different surface prep and access to their secret sauce. See Doug Turnbull and his website for what can be done by a master craftsman. The Italian Old West Replica folks also do a good turn on these but I suspect use chemical stains to reach a similar result on modern steel alloys.
Now, this is strictly an observation that you might want to play around with. Once, I was restoring an 1894 Krag from a bare receiver that had a rusted and discolored sideplate and gate. After cleaning and rust removal for these two parts and lightly polishing these, I applied OxPho blue gel using directions and gently heating the metal parts as a temporary expedient. However, what I got was a swirling purplish/bluish/blackish chromatic effect very much like case hardening colors. My suspicion is that perhaps I used accidentally a gun oil with silicone after the initial 1st attempt which sealed some parts of the steel and did not on other areas. It could also be a difference in the carbon composition of the steel with perhaps a higher degree of carbon that affected this. Recently, someone was trying to cold blue an old Mauser 1909 Argentine barrel on the THR and was having similar problems that resembled what I saw.
If you had scrap steel of a similar type (at least at one time, you would get some regulars on Winchester, Colt, etc. forums that would discuss steel composition etc. of receivers, barrels, and the like) you might be able to come up with your own formula using something like OxPho blue or other cold bluing chemicals that stain the surface combined with your own secret sauce, application, and polishing techniques that resembles case hardening good enough for light use.
