Hello Aaron,
Being a woodworker you will understand the difference between quarter sawn and slab sawn. Most gunstocks are quarter sawn to optimize strength and figure. Quarter sawn wood creates end grain. End grain in dried wood will tend to absorb or wick moisture. You will notice that plank wood has the ends sealed to prevent moisture wicking.
If the end grain on a stock is not totally sealed it will wick moisture naturally, many a duck hunter using an older Remington can attest to the stock swelling ahead of the buttplate. The endgrain at the head of the stock will absorb and wick Oil into the center grain causing the wood to weaken and turn black.
Acetone will remove surface oil but wont pull the oil from the center grain. This requires heat and a chemical to emulsify the oil. If you do not remove most all of the oil it will resurface with time.
A simple way to draw out the oil is with a heat gun and alcohol. Strip the wood, wipe down with alcohol. Apply heat to the stock and the oil will come to the surface. When the oil starts to bubble, wipe it off with an alcohol soaked towel. It takes a lot of time but it is a gentle way to pull oil without damaging the wood. Be careful not to start a fire or char the wood.
Brad
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