I have a small bottle of sperm whale oil that came with my sextant. Besides being almost impossible to get these days because of the endangered status of whales, it is an extremely light, thin oil. I would think that it would not offer much protection in hard use, when heavy parts are moving against each other, or during recoil. It works well in a sextant, because we handle it gently and move it slowly. Lives can depend on the sextant or the double rifle, but the uses are so different.

Take care, Tom