Any straight oil finish is a very poor barrier against water fenestration. 'Oil finishes' aren't very much better. To achieve some semblance of a moisture barrier, one needs to use a barrier finish such as varnish, polyurethane, lacquer, etc. Good old fashioned spar varnish remains my favorite. It is more flexible than polyurethane and hence resists crazing from repeated wettings when in the hunting fields as the wood expands and contracts (and it will). 8-10 coats, sanded between coats, and ending up with a smooth glassy finish is the goal. Then rub it out with rottenstone (or even 0000 oil-free steel wool) and it'll look for all the world like a "hand rubbed" oil finish, only with about 20 times the moisture resistance.
Regardless, after completing an oil finish, be sure to wax it with a good cabinetmakers wax. That is what will give you a semblance of moisture protection, not the oil in the wood underneath it.
It's what works for me, and merely my personal approach. YMMV.
