Proof Research Savage Pre-Fit Threaded Barrel Carbon Fiber .300 Winchester Magnum 24in 1-10 Twist 5/8-24 Thread 5 Groove. Your barrel will arrive threaded and chambered for an easy install just spin them on set the headspace with gauges and tension the barrel nut. Savage Pre-fits have either a large shank or small shank and must be matched to a large shank or small shank action respectively. To determine which action you have measure the length of the factory barrel nut. Factory large shank barrel nuts are 7/8 long and small shank barrel nuts are 5/8 long. Note that small shank barrels will also fit various aftermarket actions such as the Zermatt and American Rifle Company when used with a barrel nut. Specifications for Proof Research Savage Pre-Fit Carbon Fiber Threaded Barrel: Manufacturer: Proof Research Threads per Inch: 5/8x24 Gun Type: Rifle Flutes: No Condition: New Barrel Shank Diameter: Small Package Contents: Proof Research Savage Pre-Fit Carbon Fiber Threaded Barrel Proof Research 130704: Savage Pre-Fit Threaded Barrel Carbon Fiber .300 Winchester Magnum 24in 1-10 Twist 5/8-24 Thread 5 Groove