Nothing really will replace hot caustic blueing, but preperation and polishing of the metal is paramount, degreasing is also all important.
If you can live with a semblence of parkerization this products is
real simple to use and gives very good results as long as one follows
their directions. Clean the metal degrease well and immerse the parts
for recommended period of time follow their directions and you will have a blackened rifle.
I have used it for a number of guns and parts.
http://www.caswellplating.com/kits/black.htm
Sylvan
S/SP