I don’t have To kiill a king, but the Swedish Salas rule allows the Swedish musketeers to “fire when charging.”
So paint strict attention to the turn phase the defenders closing fire is after the chargers have moved. So this to me means that since the salvo fire is part of the charge move the salvo comes before the closing fire.
Not sure on this. Just best guess. But if the salvo fire is before defensive closing fire, it seems like the charges should either have a movement penalty (1/2 move if they fire in the charge), or a minus one to hit for shooting while moving/charging.