The OP's question was about his stock in the extreme cold. I really doubt anyone not very accustomed to extreme cold is going to want to spend much time outdoors shooting a rifle in it, so I am inclined to say "don't worry about it."
But I once saw an expensive (plastic) suitcase get dropped off a tailgate after being in minus 50 for about an hour, and and the thing shattered in a thousand pieces. So I guess if I was really serious about shooting in 25 below I would try to find out what that particular stock material will take.
