It's a gun oil but is said to be a multi purpose oil. HRP Protects Guns (also dissolves traces of copper, lead, brass and black powder residues) Neutralizes Acids and Acidic Residues Emulsifies with Water for Dilution, yet Holds its Properties Protects Wood, Leather, Plastic and Rubber Use as Marine Lubricant
Yes, I use it on my guns. Designed in 1905 by the Imperial German Army and used by ze Germans until 1945. It does have a distinctive odour though.
Black Powder firearms are different than modern smokeless propellant, need to be cleaned right away. Soapy hot water works well, Ballistol is good stuff for that, also preserves leather slings and won't harm wood stocks. I think it's a coal-tar derivative or something like that. Best "Gun Oil" or preservative/cleaning agent is about as contentious as motor oil discussions. Hoppes #9 sure smells better than Ballistol!