Proof Research Terminus Zeus 6mm ARC Threaded Rifle Barrel Competition 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 Terminus Zeus 6mm ARC Threaded Rifle Barrel: Manufacturer: Proof Research Caliber: 6mm ARC Projectile Caliber: .243 Caliber Barrel Material: Stainless Steel Barrel Twist Rate: 1-7.5 Firearms Threads Per Inch: 5/8x24 Gun Make: Terminus Gun Model: Terminus Zeus Gun Type: Rifle Package Contents: Proof Research Terminus Zeus 6Arc Threaded Rifle Barrel What firearm models does the manufacturer say Proof Research Terminus Zeus 6mm ARC Threaded Rifle Barrel is compatible with? The manufacturer suggests that Proof Research Terminus Zeus 6mm ARC Threaded Rifle Barrel is compatible with Terminus ZeusProof Research 155790: Terminus Zeus 6mm ARC Threaded Rifle Barrel Competition 26 in 7.5 Twist Pxt 5/8-24 Thread 7.5 Weight Silver