Ballistol is a lousy rust inhibitor if there is any humidity present. got a nice palm print on a rifle barrel that I put up right after slathering in ballistol and being stored on the wall in a room between 50-55% humidity, monitored. I also get brown patches after 2-3 days of drying the bore and coating with straight ballistol. It has a purpose in "moose milk" for keeping steel from rusting while cleaning powder fouling with water, and also for helping dry the metal afterward, but after that it needs to be wiped off and a real preservative type oil, grease, or wax applied.
I'm sure a zillion Ballistol fanbois will dogpile this comment and claim it's the best thing ever invented, makes them shoot 10X scores and prevents warts, but like most things it has limitations and climate has a lot to do with those.