Proof Research Defiance Ruckus 6.5mm Creedmoor Threaded Rifle Barrel Cometition 26 in 7.5 Twist Pxt 5/8-24 Thread 7.5 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 Defiance Ruckus 6.5mm Creedmoor Threaded Rifle Barrel: Manufacturer: Proof Research Color: Silver Caliber: 6.5mm Creedmoor Barrel Length: 26 in Barrel Twist Rate: 1-7.5 Barrel Profile: Competition Firearms Threads Per Inch: 5/8x24 Gun Make: Defiance Machine Gun Model: Defiance Ruckus Weight: 7.5 lb Gun Type: Rifle Package Contents: Proof Research Defiance Ruckus 6.5Cm Threaded Rifle Barrel What firearm models does the manufacturer say Proof Research Defiance Ruckus 6.5mm Creedmoor Threaded Rifle Barrel is compatible with? The manufacturer says that Proof Research Defiance Ruckus 6.5mm Creedmoor Threaded Rifle Barrel is compatible with Defiance RuckusProof Research 155554: Defiance Ruckus 6.5mm Creedmoor Threaded Rifle Barrel Cometition 26 in 7.5 Twist Pxt 5/8-24 Thread 7.5 Weight Silver