there are several different ways to do French grey .
normally what i do is cold blue , then bring the blue back with either naval jelly or Bleach . Bleach you have to be careful with because if you rub to hard , the heat generated will produce a green color .
In this case i brought the blue back with muriatic acid . Slowly reducing the blue by lightly wiping with a cotton ball in long strokes so as to get an even finish , then neutralizing with baking soda .
here is another photo of the barrel prior to the stock being finished
