Ventriliquists Firearm

When this spell is cast upon any firearm, the sound of the next shot can be thrown to any point within 75 feet, centered on the firearm, and it will give any person searching for the shooter disadvantage against sound-based triangulation, in addition, if the sound is placed right next to any person, it will either wake them from any sleep (if the sleep is magic induced, roll against the spell save DC of the person who induced the sleep) or it will daze any awake creature and do 1d4 thunder damage to the same creature, since the sound would most likely rupture the target creatures eardrum(s), the save to negate the Dazed effect and take only 1 damage would be a CON save, but it would depend on the size & sound of the gun:

Palm Pistol = DC 11
Pistol = DC 13
Musket = DC 15
Pepperbox = DC 17
Blunderbuss = DC 19
Bad News & Hand Mortar = no save

These are examples for a spell specifically designed for a fighter subclass called Gunslinger multiclassing one level into Sorcerer or Wizard, but, your DM should choose their own DC's if these seem unreasonable to them

All firearm examples used in this spell are taken from the dnd5e *******, under the homebrew page is the class gunslinger, and there is a link to the firearm properties within that site