Really just about any adhesive remover or solvent should do the trick. Sometimes old tape adhesive can be pretty stubborn so you may need to use something fairly aggressive. Probably start out with some goo-gone. If that doesnt do it then try brake cleaner, if still no luck maybe lacquer thinner. I dont think any of these will hurt the bluing but i would probably remove the action from the stock to prevent any unwanted finish damage. After you are done i would use your favorite gun oil on the bluing, burchwood casey makes a product called barricade which also works nice on blued surfaces. Good luck.