Proof Research AR-10 6.5mm Creedmoor Threaded AR Barrel Standard Standard 18 in Gas Length Rifle+1 7.5 Twist Pxt 2.15 Weight Silver. PXT - PROOF Exponential Twist - is a complete rethinking of conventional rifling geometry and twist progression engineered to reduce engraving force minimize throat erosion and create a smoother transition as the projectile engages the rifling. Specifications for Proof Research AR-10 6.5mm Creedmoor Threaded AR Barrel: Manufacturer: Proof Research Color: Silver Caliber: 6.5mm Creedmoor Barrel Length: 18 in Barrel Profile: Standard Gas System Length: Rifle +1 Length Barrel Twist Rate: 1-7.5 Gun Make: AR Platform Gun Model: AR-10 Weight: 2.15 lb Gun Type: Rifle Package Contents: Proof Research AR-10 6.5Cm Threaded AR Barrel What firearm models does the manufacturer say Proof Research AR-10 6.5mm Creedmoor Threaded AR Barrel is compatible with? The manufacturer says that Proof Research AR-10 6.5mm Creedmoor Threaded AR Barrel is compatible with AR-10Proof Research 157541: AR-10 6.5mm Creedmoor Threaded AR Barrel Standard Standard 18 in Gas Length Rifle+1 7.5 Twist Pxt 2.15 Weight Silver