Mike - I'm just going to take a shot at this here, it is hard to say without the piece in front of me. I going to guess that you have it cleaning stripped, with the mechanism, barrel, etc. all removed from the wood parts. I will also assume that you have cleaned all powder residue from in front of the reciever (around the piston), and the trigger assembly. Solvents and cleaners could redissolve anything in those areas and contaminate your finish.
This could be an easier fix than you think.
Most of the older military stocks I have seen were finished with some kind of modified lacquer or varnish, then they were often touched up by someone in the armory with linseed oil from time to time. Moreover as they wore, they picked up a generous dose of all manner of barrel cleaners, solvents, and lubricants just like your other guns.
The cleaners, ground in dirt from wear, and deteriorating age of the finish cause it to break down and the resins to become brittle. When the resins become brittle, they are a snap to sand off - unless in your case you have residual oils, dirt and many other contaminates in the mix. My experience in refinishing would lead me to believe that the pores are probably clogged with the old finish, not sanding dust.
This is the way to get that stuff out. Go to a paint store (HD may have this stuff) and get the Bix stripper in the orange and black can. It is called something like K5 or similar. Look for the orange in the label. Don't substitute one of those organic removers or orange oil products - they don't work. The Bix on the other hand should lift off the finish easily, but wear gloves and work with it outside. It will easily burn your skin as well.
Get yourself a about half a gallon of clean sawdust. Not planer shavings, not chainsaw chips, but sawdust. One of my refinishing buddies gets his from a guy at HD that runs the cutting saw for sheet goods if you need to find some. Make sure it is clean - no cig butts, nails, pieces of wire, gravel or anything else.
Put the stripper on one piece of the wood and wait about 10 minutes. You may need to re-wet this, don't let it dry out. Put some of your sawdust (this is your deep cleaning abrasive) on the wet wood, and scrub hard with stiff brush. You won't believe how much stuff will come off. With a stiff brush and plenty of elbow grease, that you can clean those pores out completely.
This is exactly how I refinish doors on site. I don't dip them, steam them, heat gun them... nothing but stripper, sawdust and stiff brushes (like a tile grout brush).
You may need to do this more than once to get the wood really clean. A couple of tips; try to time the how many minutes you leave the stripper on in each area you work. This will help you keep the wood from turning out different colors when stripped. DAMHIKT. Same when scrubbing.
Allow the cleanly scrubbed stock to dry thoroughly. Soak a rag to just before dripping with lacquer thinner and wash off any residue of gunk, stripper, dissolved stuff, and anything else from the stock. Let it dry (10 minutes). Wash again if needed.
Sand to the desired grit. Clean with lacquer thinner one more time, then apply your finish.
So tell me. Is this a newer repro from someone like Springfield Armory or is this the real deal from late 50s/early 60s? When I had a chance to buy one a few years ago, I didn't, and now I never see them anymore except with the composite and fiberglass stocks. Still kicking myself in the ass as all it came down to was the fact I didn't want to let go of the dough and I didn't want to pay for the ammo.
Robert