Backfire

You shout a battle cry and then you target any firearm that is currently loaded with ammunition. The next time the targeted firearm is fired, the attack roll automatically misses, and the bearer of the weapon is subject to a d4 roll: on a 1 the target weapon explodes completely and is unusable, on a 2 the weapon jams and doesn't fire until un-jammed which takes an action, on a 3 the weapon blasts a shrapnel shot in a 15 foot cone, everyone in the cone must make a DC10 dexterity saving throw or take 1d4 piercing DMG, on a 4 nothing happens to the firearm or the wielder but the attack roll doesn't do anything. The curse can be dispelled using dispel magic or any of curse remover.