Metals will contract (shrink) when cold, water on the otherhand expands. As far as sabots go I have no clue what they do except most plastics get more brittle when cold. Just for giggles try keeping your bullets in a pocket that isn't warmed by your body heat and see if that helps. They should "shrink" as well.

I have never worried about cleaning in a hunting situation so the patch problem I can't answer. My only guess would be try to clean as soon after firing so the barrel is still warm from the shot.

Doubt I helped but I felt like typing