A firearm suppressor is adapted to convert from an over-barrel configuration to a muzzle-forward configuration. The firearm suppressor includes a core assembly that has a removable expansion chamber that can be included in the over-barrel configuration and removed in the muzzle-forward configuration. The firearm suppressor can be converted from the over-barrel configuration to the muzzle-forward configuration by removing the core assembly from a first hollow sleeve, removing the expansion chamber and inserting the core assembly into a shorter second sleeve.