I had a PM asking some questions about preparing barrels for bluing and thought I would start a thread on how I go about it. There is more than one way to do good work, these are my techniques. Input from on others on the way they approach things is always welcome.
Before I begin polish I measure things up on my barrel wall gauge to determine the condition of the tubes.
Here is a picture of some of the tools I use.
Learning to polish metal requires a bit of patience, it is not a really hard task, just laborious but you do need to develop some skills. You want to avoid rounding your edges and washing out any engraving, sharp contours or lettering. Pitting has to be approached over much larger area than the pit itself, if you just polish the pit out you end up with a low spot that looks terrible. This is where striking or re-striking comes in.
When I re-finish a set of barrels I begin by removing the blue with paper on a backer like the concave rubber one pictured. I like this method as any dents, dings, pits, rivels, bulges etc. stand out and this is the time you want to address them.
High spots I address first, pounding them down around a mandrel as needed. Large bulges can be a real problem but smaller ones are often simple to repair.
Once I have most of the finished removed I start looking at any imperfections then decide my course of action. Very lighting pitting can often be removed with 240 grit on a rubber backer and be ready to move on. On areas with deeper pitting, dents have been worked in the past, deep scratches etc. I begin with a file. I use a 8" mill bastard with the edges broken on a belt and a smooth cut half round file. When I start work on one of these areas I work the radius well to each side of the problem so not to get a flat spot on the curve. I also start my file stroke several inches before and continue it on several inches after the problem in order to not get a low area. The idea is that you feather out any work you do over a long distance.
Once the file work is complete I progress on using paper on a backer and the mold maker stones pictured above. The stones are a semi-soft aluminum oxides which breaks down as you use it and can conform to the shape your are polishing. I try to start with as high of a grit of paper or stone as I can get away with. It is a trade off, more course grit cuts faster but leaves deeper scratches you have to remove later. I use more 240 grit than anything else to remove pits and file marks.
How high of a polish is dependent upon the type of rust blue you do and the finish you are trying to obtain. Some people rust very aggressively and if that is the case you do not need to polish much past 320 grit in my opinion. On the majority of the work I do I polish to at least 400 grit and then bland out with a fine .003" wire wheel and oil.
The small wire wheel picture above fits my Foredom tool, basically a fancy dremmel. It works very well for removing bluing on matted ribs.
The hobby sticks polishing boards are handy and come in numerous grits.
For lettering and engraving I polish "up to and around" it, then just a very light blending pass of my final grit of paper. If the engraving or lettering is damaged or pitted then I polish below the damage and have an engraver re-cut the area.