Due to a process called Single Point Cut Rifling, these replacement barrels have an exact twist and a more uniform bore and groove. These barrels are pre-lapped before rifling and finish-lapped after rifling. This black .308 Win barrel is 20" in length with no thread and fits Accuracy International AT/AX short action rifles. Accuracy International AT/AX .308 Win 20" Barrel 1420062BL