There are several reasons someone would remove the bluing from their firearm. It can be done so scratches in the frame can be buffed out without having to do spot repairs to the existing bluing. It can also be done to change the finish from blued to parkerized or plated finish. It can also be done just to repair an uneven blued finish. It is possible to remove the bluing from your firearm with products you probably already have in your home.
Brake cleaner or isopropyl alcohol
White vinegar
Deep glass dish
Clean rags
Foil-lined cookie sheet
Extra fine steel wool
Gun grease
Disassemble the entire firearm, and set all blued pieces together. Do not just field strip it.
Wipe down all blued parts with brake cleaner or alcohol to remove any oils and dirt. Set them in the glass dish.
Pour enough white vinegar to completely cover all of your gun parts. The parts will begin to turn orange after approximately 15 minutes. Don't worry, the rust appearing is only from oxidation of the metals in the bluing.
Remove the parts from the vinegar every 20 to 25 minutes and wipe down the oxidation. Continue to soak the parts until all bluing is removed.
Remove the parts from the vinegar once all bluing has been removed and dispose of the vinegar.
Return the parts to the glass dish and rinse them under the faucet to remove any remaining vinegar.
Dry the parts off as best as you can, and then place them on the foil-lined cookie sheet.
Heat the oven to 250 degrees Fahrenheit and bake for about 20 minutes.
Remove the parts from the oven and let them cool.
Inspect the parts for any rust spots, and rub the entire part down with the extra fine steel wool. This will ensure you get an even finish when you refinish your firearm.
Coat the parts in a light layer of gun grease to prevent any rust from forming. The grease can be quickly removed before refinishing.