I have personally seen it happen on a 10 day moose hunt living in a tent camp. It rained everyday almost and one of the guys had his wood stock warp. He was carrying a Weatherby Mark V, not a low end rifle. He clued in to it when he missed a shot at a grouse's head. We checked his zero and it had shifted badly. You could clearly see where pressure points had developed. The next year he had a synthetic stock.