Can I say that over many years of bluing and browning barrels I have found that the people who did this for a living devised methods of doing things to make their life at work easier, and not wanting to reinvent the wheel myself I copied there methods so here are a couple that will help anyone be more successful rust bluing.
Plug the barrels, clean out the extractor holes to remove any oil, prevent the browning solution from reaching places where you do not want it to go i.e. the breach end of the barrels and in some cases the barrel flats. Degrease the barrels properly.
For plugging the barrels use laboratory rubber bungs because they are not affected by heat, boiling water, or the rusting solution. But if you just plug the barrels there is a chance that the pressure build up inside the bores when in the boiling water could pop the bungs and allow water to enter the bores, and if there is any oil in them contaminate the water.
So to prevent this their solution which also cured another problem which is holding and positioning the hot barrels for carding.
Each rubber bung had a hole through the centre being a tight fit on an Iron rod which was threaded at each end. This rod would travel the length of the bore and extend past each bung by about four inches, a metal washer was placed next to the bungs with a nut at each to keep the bungs in place also compressing the rubber preventing water seeping past the rods. (1/4 inch threaded rod works just as well and can be purchased in standard lengths) fitted on the ends of each rod is a wooden handle to hold the hot barrels without burning your hands. To complete things a length adjustable wooden stand with six inch uprights at each was used to lay the Iron rods on that extended from the barrels so they could card the barrels top and bottom, also in the uprights a narrow slot was cut so the rods could drop into to enable the barrel sides to be worked on as well.
To keep the rusting solution off areas they used a Shellac/Pitch/Alcohol based mixture brushed on which was fast drying boiling water resistant and easy to remove.
Degreasing was done with a caustic mixture rather than solvents possibly because the action was to saponify the oils and greases, this usually consisted of a strong solution of Sodium Hydroxide (this is extremely caustic and will cause chemical burns) a less caustic solution is made from Sodium Carbonate (you may know this as ‘washing soda’) each works well if you submerse the barrels in the solution.
And just my personal preference I always card with steel wool I have tried using a fine wire wheel but it sometimes produces a patchy finish.
Finally the water you must use Distilled, Demineralised, Rainwater. Rainwater was preferred here possibly because it was free and we do have rather a lot of rain over here in Brit land.
Try to settle on a couple of rusting solutions and practice with them my personal preference is one solution with Mercuric Chloride and one without, the Mercuric chloride does speed up rusting especially if you have a dry atmosphere. Though better still by the book the reprint is not costly ‘Firearm Bluing and Browning by R.H. Angier’ and formulate your own personal mixture for the atmosphere where you live.
