Free: Contests & Raffles.
From the stand point that the previous comments were generalized, and did not cover the specific issues with stocks. Barometric, Humidity, Temperature affect wood, but unless you at +120 or -50 true sythetics (not molded plastic) the affect is almost zero. The affect on bullet flight is much greater then the affect on accuracy from the rifle. Just a difference of opinion nothing intended to offend.
I just don't see how a piece of dry wood that is sealed with stain can absorb moisture. I coulde see a little shrinkage on synthetics in extreme cold but not anything we experience here in WA.