Thank you, gents, a very good discussion.

Chuck, can you go a bit deeper into the circumstances of seeing gradiant carbon content to the depths you indicated? Gun parts? I don't disagree, but would like to know more. I certainly agree 100%with the gradiant concept, but am surprised at the 0.050" number. 2-p, any input on depths likely for guns? I've heard of depths to 0.150", but only under very special circumstances.

DDA