There are two schools of thought on this one. I personally shoot mine off at the end of the day, clean the rifle and start fresh the next day. That way I know I am starting on a clean, dry, charged as the same as the day before kind of rifle.

Others, and I used to do it myself, leave the rifle loaded. They pull the cap. Put the rifle in a place where the temperature will not vary greatly from the temperature you were hunting in all day. If the cold rifle warms up, it can cause condensation which can and will sometimes effect the powder charge and the ignition charge as well. To store it over night I take a piece of cotton cloth and set that on the floor. I then store the rifle in a corner muzzle end down. That way any condensation moves away from the powder charge into the cloth. I pull the primer and lay a piece of cotton cloth in the breech and close the breech on the cotton. This is supposed to absorb anything that might condense there.

Just for the record, I have stored a loaded rifle after hunting all day in the wood shop (unheated) a few years back. The next day, the rifle failed to go off on the first 209 primer. It did fire on the second 209 primer. Would have the rife went off the day before had I needed it, I guess we will never know.

Others store their loaded rifle for the entire season in constant temperatures and claim no ill effects for their effort. I just trust my rifle more loaded on a clean barrel and a clean charge... all a matter of preference. One other thing, if you do store a loaded rifle, put a red bandanna through the trigger guard and advise all, that it indicates a loaded rifle and is not to be messed around with.... it also reminds you in the morning ..