When someone says an unloaded gun is an expensive paperweight, what they mean is if you go to use a gun when you need it and it is not loaded then it's no more useful than a paperweight.
Yes it is chamber a round and shoot. Its only no use a paperweight etc if you have no ammo. If a loaded firearm is no use why do the military for example carry unloaded when on base why not just lock it up in the armoury. I will answer for you its because they can load it and use it if necessary. It might take a second to load it but that doesn't make it useless.