Sturdy steel rod slips into the upper receiver to give needed support for barrel changes and parts installation. Makes removal and installation of barrels, flash suppressors, gas blocks, and handguards much easier. Designed to be gripped in a bench vise so that the rod is either horizontal or vertical. The upper receiver is then slid onto the rod and the rod’s integral splines enter the barrel extension and secure the barrel extension from turning, allowing all the torque from barrel nut wrenches to go directly into the barrel extension. Unique design can't mar the barrel’s exterior finish and eliminates the need to remove sights or optics when installing the barrel on the upper receiver.