I use LSA. I think that is a military acronym for “Lubricant, Small Arms.” Used to see it in little green squeeze bottles at all the surplus stores and gun shows but it’s hard to find now. I bought three quarts of it from Sarco a few years ago, and expect that will be a lifetime supply.
Someone above stated something to the effect that petroleum products don’t dissolve black powder residue, etc. I use a good black powder solvent followed by warm water and maybe some Dawn, then dry everything and apply the oil. You don’t use it for cleaning, but apply it after cleaning as a surface protectant. I always wipe the bore before the first shot to remove any oil, and pop a cap or two on percussion guns before loading to blow out the flash channel.
I tried Bore Butter as a surface protectant per manufacturer’s recommendations, but found it gets gummy and turns brown in a surprisingly short time. No major problems with it, but I like LSA better.
I’ve been doing this for quite a while with no rust or oil-related problems. LSA does not evaporate or oxidize. Guns that have been wiped with it, inside and out, are good for years in storage.
Best regards,
Notchy Bob