Ive used Formbys Tung Oil before, and liked it. After reacquiring a gun I sold that had that solution applied, I found it yellowed a little, which was a little disappointing.

Some like to use multiple applications of was, such as Briwax or Renaissance.

Something I plan to try is clear Ceracote. By adjusting the amount of hardener, you can vary the degree of shine, and its a strong finish that will not yellow.