I used to pull shipping pallets out of the surf in Florida to recycle for furniture repair. The pallets were usually Mahogany, Ironwood, and often Teak. As they were in the Gulf Stream, the time in the tropical water was no more than a week or two at most. I would break them down and wash them off well then air dry in a open air shed "out of direct sunlight". A mahogany 4X4 would dry to the point I could plane them in about three weeks. Usually 1/8 to 3/16 was enough to get below any damaged wood. This was raw unfinished lumber. I have to believe that a well oiled gun stock would fare much better.
I hope this us useful.