No need to plug anything,,bore, chambers, screw holes,,,,anything.
The only thing the cylinder is going to be subjected to is boiling water.
Older firearms that were rust blued sometimes show interior surfaces on the action and parts that are nicely polished and 'in the white'.
This is because those interior surfaces were difficult to rust blue (carding in particular). So those areas were avoided while applying the soln,,some sloshed over onto them but not purposely.
When the job was completed, those unblued surfaces were 'benched' as the term goes,,polished and left in the white on higher grades.
It left a spectacular look.
Simply left as-is on lower grades with the metal taking on a grey tone from the bluing process ( traces of bluing soln in the boiling water tank) and the slight over lap marks of the bluing into the insides of the action and parts.
With the advent of Hot Salt Bluing in the US (late 30's),,the immersion of the parts in the bluing tank simply blued every surface inside and out. They were then just left that way,,blued. The days of polishing out the interior of the actions was over except on the very high grade guns.
Do Not swab the internal surfaces like the bore and chambers with the rust bluing soln. Just leave them as you find them.
No need to 'blue' them.
Clean those surfaces before the bluing process to remove any oil or contaminants that may spoil the entire re-blue process.
Oil in the boiling water is one of biggest causes of a spoiled rust blue job.
Even the tinyest amt on any of the parts that makes it into the boiling tank will immediately thin out from the heat of the water and spread over the entire surface of the water in the tank.
It'll be on the part as you pull it out,,it'll get on the carding wheel or steel wool you use to card the piece, it'll still be on the part when you re-coat it for the next cycle. The contamination will spoil the color, add streaks to the bluing and the bluing will tend to be weak and wear off quickly especially at the edges.
The water will have to be changed and the tank cleaned. The carding wheel cleaned. Throw the steel wool away and start new. It should be degreased anyway as new stuff usually has some oil in it to prevent it frm rusting.
Pour some of your bluing soln into a smaller container for that job and work out of that. Never pour the un-used stuff back into the big bottle. It will have some contamination to it once you start to use it out of the smaller container and pouring it back will spoil to whole bottle.
When you pull the part(s) from the tank,,shake them off of the hot water and let them air dry.
If you are slow rust bluing, let them cool down before carding. Gently weep any water from crevices with a twisted bit of paper towel. Don't let water dry on the parts.
Dry swab the chambers/bore at this point if you want to. They should be clean and clear.
Card the now blacken parts,, then recoat with bluing soln.
Do not recoat them if they are still hot.
>If Express rust bluing, you'll have to pull the part(s) from the water and quickly shake the excess off and get those extra drops off of them. Then immedietely card the parts. Then immedietely recoat them with the Express rust blue soln while still hot.
If the parts cool off too much, you can reheat them carefully with a propane torch or the old method of simply putting them back in the tank to heat up.
'Baker Formula' & 'Belgian Rust Blue' are probably the two most common terms for Express Rust Blueing. Both will give you a lot of info if you choose to go that route instead of the Slow Rust Blue method.
I use both,,the Slow Rust most of the time. But an Express Rust blue has it's advantages in certain instances.
I use 'Laurel Mt'n Rust Brown' soln for Slow Rust Bluing (Rust Brown sent through the boiling water tank comes out Rust Blue)
For Express Blue I use 'Mark Lee Express Blue'.
There's also a Mark Lee Express Rust Brown soln I believe, but I have never tried that for bluing.
I stay away from any of the older solns that had Mercury compounds in them (Mercury Bichloride usually). Most did and they worked very well,,but they didn't do me much good these years later. I probably used just about every one of them put up on the market from the late 50's on. The two listed above work just fine, have no Mercury in them and I've never had any complaints from customers over the years.
Brownells sells both of them. Even a small bottle last a long time (if you don't tip it over!)
Slow rust blue soln is different from Express rust blue soln. They are sold as such.
Plugging bbls and chambers can be done, but it's not necessary.
It adds an extra step for no reason. I've never plugged to bores on any I've rust blued in the 45yrs I've been rust bluing. That includes everything from STAR pistols to Purdey shotguns.
..One exception would when I do a Damascus finish on shotgun bbls,,I still don't plug the bores but I do protect the bores with a heavy coating of common shellac applied with a simple swab. Nothing fancy, just 3 or 4 coats and let it dry real well.
It's to protect the bores during part of the Damascus finishing process where the bbls have to go into a Ferric Chloride dunk for a few seconds to help bring out the Damascus pattern. The F/Chloride etches the surfaces very lightly and it's not something I want to happen to the shiny bores of the shotgun as well as the outside of the tubes I'm working on.
The shellac holds up very nicely even through the boiling water of the process to get the black of the black&white damascus patter to show. I do usually reswab the bores at about cycle 8 or 10 to make sure.
Damascus finishing take many more cycles of the rusting/boiling as the etching dunk in betw removes some of each time. Kind of 3 steps forward and 2 steps back each cycle. So 12 or 15 cycles to finish a Damascus pattern bbl as opposed to 5 or 6 to do a simple rust blue steel bbl.
On a revolver, I pull the bbl to avoid any trapped oil or grease from weeping out from the threaded joint of the frame/bbl during the bluing process and spoiling the job. It's generally packed with some in there and the heat will allow it to spill out leaving an unblued or poorly blued area right at that joint.
Not a given that it'll happen, but I learned early on that was a distinct possibility so it's just part of the process for me.
But everyone has their own techniques and whatever you end up feeling comfortable with and gets you the results you are looking for,,that's the method you should stick with in your work IMO.
There's no wrong way to do this, just a lot of different ways to the same end. Some will give varied results over others but the basic process of rust bluing remains the same.
