Franklin Armory F17 X Upper Features The Franklin Armory F17 X upper is built around a proprietary gas system designed specifically for the .17 WSM cartridge using an OPS piston and low profile gas block rather than a direct impingement system prone to reliability issues with rimfire pressures. The 16 inch barrel carries a 1:9 twist rate tuned to stabilize .17 WSM projectiles for consistent repeatable accuracy at extended rimfire distances. A standard bolt carrier and charging handle keep the upper compatible with common AR-15 lower receivers simplifying installation for shooters building out a dedicated rimfire upper. The 1/2x28 threaded muzzle ships with the Aura muzzle device installed giving the upper a complete ready-to-shoot profile. The 15 inch handguard extends the shooting platform with an integrated barrier stop for stability when shooting from cover or a rest a valuable feature for varmint hunters and target shooters alike. Its optics-ready design allows a full range of red dots and scopes to be mounted directly giving shooters flexibility to configure the upper for their intended use. Finished in black the F17 X delivers a clean purpose-built rimfire upper without unnecessary bulk or added weight. For AR-15 owners looking to add a dedicated .17 WSM capability to an existing lower this Franklin Armory upper is a complete well-engineered solution. Franklin Armory F17 X Upper Specifications Manufacturer: Franklin Armory Model: F17 X Type: Complete Upper Caliber: .17 WSM Barrel Length: 16 Barrel Description: Threaded Twist Rate: 1:9 Muzzle Thread Pitch: 1/2x28 Gas System: F17 Proprietary OPS Piston Handguard Length: 15 Muzzle Device: Aura Low Profile Sights: Optics Ready Color: Black Available At: GrabAGun