Dynatek Bore Coat is the best protection against rust & corrosion. Its not an oil but a glue like mixture that you coat your bore, let it sit over night and then fire a total of 40 shots through. This special glue contains particles of Ceramic that embed into the steel of the gun, sealing it up tight from corrosion and rust. Never have to oil the gun again.
For the life of me I can't understand how fouling from the first shot does not become embedded under the magic ceramic particles that embed with the second shot (and each succeeding shot).