Abstract: An interchangeable barrel system for a firearm includes one or more barrels each having an outer surface, and an inner surface defining a longitudinal bore open between a muzzle end and an action end. The action end has a threaded portion that includes one or more tangential notches formed partially therethrough. A receiver includes one or two threaded adjustment bolt apertures that tangentially intersect a barrel port. In use, with the action end of one of the barrels threadedly engaged with the barrel port and manually tightened to align one of the threaded adjustment bolt apertures with one of the notches, an adjustment bolt is tightened to contact an end of the notch to apply a tangential force to the barrel to further tighten the barrel within the receiver and to provide a desired headspace between the action end of the barrel and a bolt of the firearm.