I've never done any color case hardening, so could be wrong, but gut instinct would make me shy away. I've done enough work with torches throughout my life to see metal go past a certain point, and change completely, becoming weak and brittle. The light colors on that gun remind me of such unfortunate learning experiences. [Note the sharp edge of the action and the fences].
I'm not saying that is the case here, and it may be the camera, but it would be a no go for me.
Jim