Okay I'll admit it I'm somewhere between just stubborn as a mule or just plain stupid.
I have tried Radocy Rust Bluing on a variety of steel grades and have always had very good results on everything but CrMoly. Every time I've attempted a CrMoly the results were somewhere between Purple Mud and Blotch City.
But ever the optimist I decided to have one more go at a pile of HPA tubes. I tried absolutely every trick I know to get a decent colour and finish but as you can see.....
HPA Tube - Radocy Bluing - 2.jpgHPA Tube -Radocy Bluing -1.jpg
IMHO Radocy does not produce satisfactory results on any 4130, 4140 (LW Barrels). You get results that are typical of oil contamination even with a 1 hour boil in detergent.
I've had good luck with Pilkingtons on CrMoly but the colour is very charcoal. Very even, uniform but lacks flash.