Just a "Dumb" Question I know but how do you get that "Chisel Hardness" on the surface of a piece of 4140 & maintain a "Less Hard Core". By design Case hardening is applied to steels not suceptible to much hardening so that hard case can go over a soft core. To draw 4140 back to a point it would not be "Brittle Hard" would also draw that Chisel Hardness out of the case. Case hardening is not normally applied (For Good Reason) to steels of above about 20 points carbon. 41"40" has 40 points.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra