I would still want to finish up with a solvent soak just prior to finishing or doing any glue repairs because I don't think you'll ever get all the oil out of a heavily oiled gun stock. Just leave a stock that you think is de-oiled sit around for a few months and watch as that dry lifeless wood slowly darkens as more oil migrates to the surface. I agree that very long solvent soaks take out more than just gun oil and probably don't make the wood stronger or more resilient to future cracking. Alternate methods like ammonia and water washes, packing the wood in some absorbent material, or using mild heat and a vacuum to draw out much of the oil are just good ways to lessen the time of solvent soaks and to reduce the oil contamination of your solvents. Lots of dirty oil dissolved in your expensive solvents is not going to do a great job, and is going to create a more frequent disposal problem.
Ken, I don't think the marinade in your vacuum packed steaks would soak in so deeply if they were in a rigid airtight vessel rather than a plastic vacuum bag that allows outside atmospheric pressure to push the juice in from all sides. But a NY strip steak on the grill sounds great for dinner tonite. Thanks for the idea.
