If muggles were to go into an all-out war against wizards not only would they far outnumber then but I do not think most wizards would be able to react to gunfire, they might be able to block or re-direct a few bullets but without any forbidden spells they can't do too much, in order for a lawful wizard to deal as much harm as a bullet they would need an entire hogwarts legacy combo, but if the humans were to find some sort of base which the wizards were using a single little boy would wipe them all out because after all the wizards are still humans and thus would still get radiation poisoning/cancer if they were to somehow be able to flee in the nick of time.