On vintage guns I think wood shrinkage has allot to do with the quality of the wood used when the gun was built....I have several 100 year old plus W&C Scotts that saw lots of use and have very little if any wood shrinkage then I've saw other guns with lots of shrinkage. Scott was known for having lots of cured stock blanks on hand.

I've heard some sellers mention glass bedding but I don't think wood shrinkage is reversible.