Chris: Nice post. You explain the real problem well. To many people, 1/32" does not sound like much. But when you are fitting pins through holes in a rifle stock, and they have to go through a hole in the barrel " hangers", that is a HUGE amount of change. That kind of shrinkage and expansion( swelling) of wood over the life of the wood occurs whether there is high humidity, or less, and regardless of the stock finish used.
About the only way to stop this kind of expansion is by using a laminated wood stock, where the laminates are layered so that they pull against each other.
Over the long life of a rifle, this kind of expansion can take place as the wood ages, too. Using a good stock finish, and wood sealer, particularly on end grain, will SLOW the process, so that it will take many years longer before you see this kind of aging on the stock. But, it won't stop the changes all together.
A good friend of mine built a CVA mountain rifle out of a kit, back in the 1970s, and he put the gun aside in his gun closet over the winter. Winters are very dry here, and when he took the gun out the next spring, to shoot again, he was horrified to learn that the balls were going all over the place. At 50 yds, off the bench, with a cold barrel, he could hit the paper somewhere close to the bullseye- whereas the prior Fall, when he zeroed the rifle, he was making a small group in the 10-X ring! His second and subsequent shots out of a warming barrel didn't even hit the paper!
I arrived at about this time, and after a discussion, he decided to take the barrel out of the stock to see if something was wrong there. He barely could get the closer of the two keys out of its slot with a hammer! When he removed both keys, and then tried to put them back, he could not get the closer key to go into its slot at all. In fact, the stock was so warped, that it was visible to us, when we finally looked. AND, you could not see day light through that keyway. He put the forward key in the stock to hold the barrel and stock together, and fired some more shots. They were all in the X ring again.
The Stock had been cut from fairly green wood, it appears, and it dried out and warped over the winter, and then in the rising humidity of the next Spring. He took the gun home, filled the screw holes for his escutcheons, relocated them, and then recut the keyways in the stock. Only a little bit of filing was done on the dovetail slots in the barrel, and on the keys themselves to make them fit in and remove easier.
