I use Mark Lee's Express Rust Blue #1. It's the same process (and probably the same product) used by Doug Turnbull Restorations. I have a homemade temperature controlled cellular core PVC stand pipe that I've modified and used for many years now. I use mine to both preheat a barreled action and blacken them after the solution is wiped on with a dampened cotton ball. When you hang a barrel in boiling water for more than a few seconds there is enough latent heat stored in it to cause it to immediately flash dry when you take it out. It stays that way for several minutes and there's no need to use a gas torch. I use tongs or tweezers to hold screws and small parts in front of a heat gun until they are 150-200 degrees Fahrenheit and then apply solution. I boil them in a cheap Mainstays pot from Walmart.What bluing/method did you use? That bluing looks incredible as well.
There are pictures of my equipment and the products that I like to use along with links to some instructional videos showing various ways to do it in a thread about an old shotgun I refurbished for a friend:
Some people like to build ships in bottles as a hobby. I've always liked to repair and refinish old worn-out, cast aside, and obsolete firearms. Lately, I've been staying busy helping an old friend restore his flood-damaged gun collection. I had shown him the shop equipment I use to anodize or...