Is it possible, or advisable, to apply tung oil over and already existing shellac finish?

I have a very nice M44 with the original shellac finish on it , but it appears to be , for lack of a better term, dry,

I was considering putting a few coats of tung oil over it, to brighten it up and protect it.
I dont want to strip off the original finish, the rifle is one of the nicest M44's I have seen.
I would just like to brighten it up a bit and protect it !
What do you think?

The shellac seals the surface. The oil would not be able to penetrate into the wood, it would just be wiped away.
If you have an oil finish you can just touch it up with more oil. That's the big advantage to an oil finish- scratches are not a problem.
There isn't any collector interest in keeping Mosin Nagants original. Why not just strip the finish and, if you want a gloss finish, use Tru Oil? I have finished a stock with Tru Oil and it looked like a high gloss poly finish, but touched up very easily.
Jim

If its really shellac, you can rub in an additinal coat or two shellac to freshen it up.   You may want to clean it first with some denatured alcohol (alcohol is the solvent to use with shellac).  That may give you the effect you want (especially if you give it a nice rub down with paste wax afterwards), but in any event will clean the surface before additinal coats of shellac.