Here on the prairies it can get quite dry in the winter and humid in the summer. The best defense is a application of linseed oilicon annually. If the original owner unwrapped it and cleaned with solvents to remove all the oils it is probably drier than a popcorn fart. Not only does linseed oilicon nourish the wood but it helps to prevent warping.
If you still do not have around 6 # of up pressure my preferred method is to apply thin shims of cork at the tip of the barrel channel, it is a easily reversed fix. The issue might be that you have a warped stock
Once you have it apart as you reassemble it with the trigger guard reinstalled, check to see how the barrel sits in the fore stock. Take a piece of paper and loop it under the barrel and move it from the knox form towards the muzzle. If it binds left or right of the barrel the stock has warped to the side, if it binds on the bottom of the barrel before you get close to the end of the fore stock the wood has bellied down. Warped stocks are a PITA to fix but they can be fixed with some careful steaming and some clamps and a jig. You have to go a little bit further as the wood tends to spring back a bit.