Gun Barrel colours

[jackalope]

I re-did a 1913 Luger that had almost all of its bluing gone and was badly water damaged to the point that the gun looked like I dug it up off of a battle field. After MUCH research I found Brownells old world rust bluing with a pinch of sodium nitrate added to it was what made the closest finish to what the Germans used back then. The process is very involved and requires a humidity/ heat box and days to do! I made the box using a cooler that I set another box inside of and then added boiling water to and closed the lid for 8 hours, after 8 hours the gun is removed and boiled in salt water for 15 minutes then it needs air dry completely before you go over the gun with 000 steel wool. Repeat this process between 4 and 9 more times to yield the color of blackness you want, in my case I did it another 7 times and the Luger was a deep dark shiny coal black blue color which is why I made my comment about chemical reaction colors in metal are VERY difficult to duplicate. No idea about the bigger stuff as I've never restored any of them.