Receiver finish

[Researcher]

Were the very deep relief engraved guns like the Whit 1s originally color case hardened? I sure don't see any vestiges of case colors in the two I've saved pictures of.

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[edgarspencer]

Originally Posted by Dave Noreen

Were the very deep relief engraved guns like the Whit 1s originally color case hardened?

Dave, while I wasn't there, it would be my assumption that all guns, irrespective of grade, were case hardened. Color Case Hardened is somewhat a misnomer, because the case hardening process is a heat treatment for mechanical properties (Tensile, Yield Strength, and hardness) The colors achieved in the process are a secondary byproduct. There are other ways to heat treat for mechanical properties, but when heat treating a finished, machined part, Case Hardening is the most practical, because the process virtually eliminates the possibility of the scale that results from either Normalize & Temper, or Quench & Temper. The temper cycle of these two processes is effectively a stress relieving cycle. Ductility, reported as Elongation, and Reduction of Area (of a tensile test bar) is inversely proportional to hardness; hence, receivers which are Case Hardened, while having surface hardness, have low ductility, nearer the outside edges. The core of the section may be somewhat more ductile, but thinner section are going to be borderline brittle (Remember the cracks of the pre-13,000 Lifters at the junction of the standing breach and water table?)
As to the absence of colors on the highly (and heavily) engraved A1 guns, I am guessing they were polished off, or eliminated in a French Gray process. I am certain they were there when the part was retrieved from the quench bath. The surface of the water table (engine turned to some) was almost certainly done after the heat treatment, and also would have removed any colors from case hardening.