Gunpowder marks and clues

Exploration Stage: Mansion by the Canal
From: Huntress
Description: Clean your pistol until it is shiny and clean. You'll need a metal brush to remove rust and lead from the muzzle. Help me find a brush with the right caliber.
Completed: Those brushes you found are perfect for cleaning pistols. It will make it easier for the ladies in town to get their pistols back in proper condition.