Arrrgh, my connection cyber ate some terrific nonsense I typed out.
In a nutshell, your reference for 8620 back on page 7 showed most performance measurements were 'typical for steel'. With the ability to look up carbon migration, can 8620 in charcoal, at maybe 1400* for maybe an hour or two, be carburized any deeper than say ten thousandths.
I think there's a reason and affect for gun CCH, but the process would not seem to be able to increase core strength. It's still the same 8620 on the inside. Industrial applications such as ball bearings or gears may be an entirely different situation with the significantly higher temperatures, much longer times and optimized environment.
I also suspect that the performance of a spring, receiver, would have a lot to do with the design. I think very little on a receiver does not act like a spring when a shell is fired. There seems to be an implication creeping in that thin case annealing will automatically cause permanent deformation of the part. It just doesn't seem to make sense if the forces of firing a shell does not exceed the material or design.
