OGC:Misfire (5e Variant Rule)
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Occasionally a firearm fails to fire due to fouling or the round getting stuck. If the d20 roll is a 1 when making a ranged attack, then in addition to missing the target the firearm is considered to have misfired. You must clear the barrel using a gun kit as an action before it may be fired again (note that the cleared ammunition may be used again). If the d20 roll is a 1 and you had disadvantage on the roll, then you have cracked the barrel and the firearm is useless until repaired (requiring a day of work with a gun kit or a use of mending).