I leave my ML in my locked truck stored in a heavy case. I load it either outside at home or when I arrive at the hunting site, depending on how close to the actual stand my truck will be parked. I have a cab on the back of the P/U and it travels there. I never bring the gun inside before a hunt or if there is a load in it.

Get a heavy-duty carrying case - it will insulate the gun somewhat and minimize the temp changes.