JMH,
I'm not as experienced as others here, but something to think about is the polishing. Sometimes steel will not color properly if polished too highly, especially if hard. I have trouble with Mauser bolt shrouds highly polished , by hand. Re-polishing with 320 grit cloth corrected the problem. If you are polishing them with a "wheel", I suggest you try a sample polished by hand, with worn 320 cloth.
Mike