Abstract: A barrel retaining system for a firearm includes a firearm receiver having a barrel nut coupled thereto and a barrel assembly, which in one embodiment may include a barrel with a barrel extension coupled thereto. The barrel extension includes a plurality of barrel locking lugs that rotatably engage corresponding locking elements disposed on the barrel nut. The barrel extension may further include a flange that may engage one end of the locking elements of the barrel nut and the barrel locking lugs may engage an opposite end of the locking elements to wedge the locking elements therebetween for securing the barrel extension to the barrel nut. The firearm may be an autoloading rifle in some embodiments.