The upper receiver is slid onto the rod and the rod’s integral splines enter the barrel extension and secure the barrel extension from turning. This allows all the torque from barrel nut wrenches to go directly into the barrel extension. In contrast, receiver vise blocks transmit the turning force into the aluminum receiver, a good part of which passes through the small, easily distorted receiver index pin. With the Geissele Reaction Rod, marring of an upper receiver’s finish by gripping and twisting inside vise blocks is eliminated and so is the need to remove sights and mounts from the receiver’s M1913 rail.
Note: The Geissele Reaction Rod is machined at Geissele Automatics’ state of the art manufacturing facility in Norristown, Pennsylvania. The rod is cut from a solid bar of 4140 Chrome Moly steel, properly quenched/tempered and ground to an exact diameter that is smooth and straight so the rod will enter an upper receiver without wobble.
*The Geissele AR10/ SR25 Reaction Rod is not compatible with the HK MR762 upper receiver.