The 45-70 is a classic example of how reloading can help. The old guns can't handle a lot of pressure. Ammo makers have to make ammo that can be shot in all guns of that caliber or they'll end up blowing up some old guns. So, they load it down. Some of the newer guns can handle much higher pressure, well above the ammo that's on the shelves. The only way to make use of the gun's ability is to load your own.
