Savage Barrel Lock Nut Lock nut to secure barrel to receiver. Screw the barrel in to set headspace, then tighten the lock nut. Precision machined to close tolerances for optimal fit, alignment, and concentricity. This nut features squared grip notches to fit a standard Savage barrel nut wrench. This makes it a great replacement for rifles with a smooth barrel nut as well as factory rifles being fitted for a new barrel. This barrel nut fits the most common "small shank" Savage rifle barrels with 1-1/16 x20 threads.