Remember Remember - D&D One shot

Some Guy has bought out all the gunpowder in the local area for some sort of plot?! Nearby gunpowder dealers are growing tense, they’ve all forgotten to source all the powder they need for this massive job and need you and your party of adventurers to find some way to generate enough fire power to make sure this goes off without a hitch. 

Bring a level 6 character with one uncommon magic item.