Interesting thread, INMHO there are only two MASTERS of case colour hardening, St ledger in Birmingham, UK and Schilling in Austria. Doug Turnbull in the US is good but you have to ask for "subdued" colours, some of his stuff comes out looking like a rainbow ! Cyanide coloring I think looks poor, best Spanish gus get sent to St Ledger (as do Hollands, Purdey and Boss). The metallurgy of an action also dictates what can be done. I had a 6.5 x 54 custom rifle made from an old Greek military mannlicher, to see the whole story click on this link
http://forums.nitroexpress.com/showflat.php?Cat=0&Number=126684&an=0&page=3#Post126684At the end we could not case harden parts of the action as the Rockwell measurements were off the scale
Still, interesting, best
