Proof Research Terminus Zeus 7mm Backcountry Threaded Rifle Barrel Sendero 16.5 in 8 Twist Pxt 5/8-24 Thread 1.9 Weight Carbon. 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 7mm Backcountry Threaded Rifle Barrel: Manufacturer: Proof Research Color: Carbon Caliber: 7mm Backcountry Projectile Caliber: .284 Caliber Barrel Material: Stainless Steel Barrel Twist Rate: 1-8 Barrel Profile: Sendero Firearms Threads Per Inch: 5/8x24 Gun Make: Terminus Gun Model: Terminus Zeus Gun Type: Rifle Package Contents: Proof Research Terminus Zeus 7Bc Threaded Rifle Barrel What firearm models does the manufacturer say Proof Research Terminus Zeus 7mm Backcountry Threaded Rifle Barrel is compatible with? The manufacturer says that Proof Research Terminus Zeus 7mm Backcountry Threaded Rifle Barrel is compatible with Terminus ZeusProof Research 156650: Terminus Zeus 7mm Backcountry Threaded Rifle Barrel Sendero 16.5 in 8 Twist Pxt 5/8-24 Thread 1.9 Weight Carbon