Proof Research AR-15 223Wylde Threaded AR Barrel Standard Standard 18 in Gas Length Rifle 7 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-15 223Wylde Threaded AR Barrel: Manufacturer: Proof Research Color: Silver Caliber: .223 Wylde Barrel Profile: Standard Gun Make: AR Platform Gun Model: AR-15 Gun Type: Rifle Package Contents: Proof Research AR-15 223Wylde Threaded AR Barrel What firearm models does the manufacturer say Proof Research AR-15 223Wylde Threaded AR Barrel is compatible with? The manufacturer suggests that Proof Research AR-15 223Wylde Threaded AR Barrel is compatible with AR-15Proof Research 155189: AR-15 223Wylde Threaded AR Barrel Standard Standard 18 in Gas Length Rifle 7 Twist Pxt 2.15 Weight Silver