Try your soln just as it is along with your rusting temp, time and humidity,,but on a plain piece of hand polished cold rolled steel. I'll bet you get some nice results.
Your Wm Powell bbls won't be far off from that anyway in how they respond.
I suspect those Walther bbl cut offs are either stainless steel of some high corrosion resistant alloy from the way they are coming out w/a grey color and less rusted as you go along.
Maybe they need an etch coating first before the bluing soln will 'take'. Maybe they'd respond to an Express Blue better,,All sorts of little things happen that you end up sorting out over time. But when starting out and wishing to do plain older steel bbls,,you certainly don't need that stuff in your way.
Less boiling time hasn't ever been a plus in my experience. They do need some time in the tank to convert.
Leaving them in an extra long amt of time doesn't seem to gain anything though. I usually let a set boil for 10 to 15min then out it comes. It's as dark as it's going to get at that point.
