y not5,
At those temperatures you won't have a moisture problem, but you will have a condensation problem if you bring your ML indoors where it'll be a lot warmer. Leaving it in the shed, uncapped should work just fine.
I hunted last weekend and the temperature was in the lower teens. I left my ML loaded and uncapped in my SUVover nightand I had no problem with the Triple 7, when hammer time came the next morning. I also used a fresh 209 primer and saved the previous days primer for a later day at the range.
Good luck and make sureyou post pictures for us.