normally i try to remove anything that can come off that isn't metal without breaking it then just soak it in oil. Gun oil is the best but i've used new motor oil i get on sale(doesn't hurt anything but just isn't as fancy and I never worked with bone/ivory before). normally i only have handguns that look like boat anchors, a rifle like that will be a bit harder to soak in tub due to size but rubbing the oil on should work and place it on plastic to keep the mess in check
