For really stubborn lead removal try a 50/50 mix of 3% Hydrogen Peroxide (the common drug store variety) and white vinegar. Plug the bore, fill it up using a dropper or syringe and let it stand for 2 to 3 minutes. (Do not let it stand for too long.) You may get some foaming so protect the barrel’s external finish as this solution is not kind to bluing. Drain and wipe out the black muck that used to be lead and then immediately clean well with bore cleaner.
Thanks to Joe Sledge for this recipe.
While most people have used this solution without a problem there have been reports of this solution pitting some mild steel barrels. The factors involved in this seem to be the type of steel, the presence of rust in the barrel, and excessively long soak times leading to chemical changes in the solution. I strongly recommend not letting this solution soak more than 2 to 3 minutes.
Pure turpentine has reportedly also been used as a lead remover.
Lead Removal Cloth
Lead deposits on the face of revolver cylinders and similar places can be removed with a lead wiping cloth prepared as follows.
Mix the following ingredients
500 gr – 400 grit or finer aluminum oxide powder
450 gr – kerosene or #2 fuel oil
4 gr – lemon oil (for a more pleasant smell)
5 gr – ammonium chloride
Evenly saturate a soft thick cotton cloth or flannel with the solution and allow to dry. (There is no reason it won’t work wet though.)
Carefully remove any very heavy lead deposits with a scraper and then wipe the remainder with the cloth to remove.
Notes: The active ingredient in commercial liquid lead remover products is Ammonium Oleate (CAS 544-60-5). It is however difficult to get. Most of the formulas are basically ammonium oleate, ethanol, and some petroleum distillates as a carrier.