Ballistol should never be used on Nickel-plated guns, because there is a film of copper under the nickel. Ballistol is corrosive to copper and will cause the nickel to flake-off of your gun over time!
Ballistol also should never be used as a long-term storage solution, either. It's an excellent cleaner, and has many, many uses, but longterm storage is NOT one of them.
See here:
Ballistol Education And Warning - YouTube
Eezox is an excellent pre-storage protectant. I also recommend Bore Stores bags from Brownells.