I had to chuckle while reading this. I'm not a gun builder but have restored countless old guns, which many times included browning all the steel parts.
I have used just about every process (solution) used to get a nice browned finish, including putting the parts in the shower letting them rust naturally from the humidity.
What made me chuckle is as a Blacksmith, if you ask 6 Master Blacksmith's a question about fixing a problem, you will get at least 10 answers (all correct) on how to fix it.
Randy aka bpd303