I would be very cautious about any "fire quenching the receiver to see if I can get a color case hardened look". The only thing I know about Case Hardening is it is not for the average tinkerer. Some of our more knowlegable members may chime in.
I think you are off to a good start!
I am going to start with small parts first. I was talking to an old gunsmith and he used to heat parts in an oven to about 500 degrees and then immediately dunk the parts into used motor oil. Then he would leave a little oil on the part in patterns and use a torch to heat the parts to get the affect.
