Remember, there's fiction here too, not just mechanics. Fiction forward. If a player narrates unloading with a blast of fire, the GM should ask if they're trying to kill the dude. Cuz that's what fiery blasts of fire do. If they're trying not to kill anyone, they need to narrate accordingly and describe what they're doing so the human isn't torched. In the books, Harry is constantly hitting people with his force ring to knock them back without killing them when a blast from his rod would be more effective, if deadly.