I don't understand the desire to chemically remove bluing from something that will need polished anyway.  It takes maybe 3 to 5 minutes to entirely remove the bluing from a barrel or action with maroon Scotchbrite or 400 grit wet/dry.  No corrosive fumes, no breathing noxious fumes, no chance of splashing into my eyes, no holes burned in my clothes or contamination of my workbench.

Here's a barrel I cleaned up last week using maroon Scotchbrite deburring sheet.  It also shows why you have to polish after removing the blue and before refinishing:

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Truth is, there are a lot of ways to skin this cat.  Old bluing can be polished away or chemically removed.  Either way can work.  This thread is about prepping for case coloring, but if it was about re-bluing it is worth noting that there is really no need to remove original bluing.  You can re-blue over old blue and it will not be noticeable as long as the polish beneath the old and new is consistant.

As AJ said, you can reblue over old without removing it.  I have successfully reblued ballards that were that awful purple from hot caustic blue, by degreasing, rusting, and boiling to put rust blue over the purplish caustic blue.  It takes several applications, but works.

I have also been able to retouch existing blued barrels that have rust speckling or spots by steel wooling the rust off, and then rust bluing them for touchup.  They don't look perfect, but usually improve a lot.

I know this is getting off topic, but ssdave mentioned touch up bluing by rust bluing an already blued part.  You really don’t have to reblue the entire part though.  A simple trick is to rust the bare spot only, then heat the area until it will sizzle water.  Then, dampen a piece of cloth, hold the dampened cloth with pliers or hemostats, and rub down the rusted area.   Like regular rust bluing, repeat until it darkens to the desired shade.  Rubbing the area with the dampened cloth provides both the steam for rust conversion and carding of the spot.

Sure shot wrote on Apr 11^th, 2025 at 4:26pm:


Way back in the mid 1970's I wanted a 1911 .45 a lot, but they were pretty spendy. I found an Essex bare frame new for $50, and there was a place back in Virginia selling complete military surplus kits for $150. So I built myself a 1911 handgun. 
I polished all the parkerizing off the various parts and gave the frame and parts to a local gunsmith to be hot blued. They came out a deep dark purple that he actually thought was neat (or pretended to think it was.) and I lived with it. The Essex frame was the only part that wasn't purple, and I suppose it was a different alloy.

Quite a few finishers use phosphoric acid as in naval jelly or Tidy Bowl cleaner to impart a French Grey finish on gun parts.

Very weak Nitric soln in water works well too as does acidic acid as you found out.

Weak nitric soln works great on Belgian mfg Brownings for restoring the French Grey finish their high grades came in.

Sometimes spot hardened areas on some parts will come out darker. The slide stop notch on 1911 slides for example.
But those areas can be toned down by careful massaging with a very soft erasure or other soft abrasive while the parts are in the soln.

None of these solns should be strong enough to harm your hands even if you are not wearing gloves,,may sting if you have a cut on them though!

Even the weak Muriatic acid soln I use to remove blue and heat scale I pick the parts right out of it and handle them w/o any gloves. It's that weak.
You don't want it to pit the steel.