Systems and methods for mounting a barrel to a firearm are disclosed herein. The firearm may include a barrel, an upper receiver, a hand guard assembly, a lower receiver, a pistol grip, a buttstock, and a trigger. A barrel extension may include internal threads, mounting protrusions, mounting apertures, an elongated front barrel extension portion, an elongated rear barrel extension portion, and a barrel extension mounting flange. The barrel extension may be sandwiched and secured in between the upper receiver and the hand guard assembly via clamping screws.