Proof Research Zermatt TL3/ SR3 6mm ARC Threaded Rifle Barrel Sendero 20 in 7.5 Twist Pxt 5/8-24 Thread 2.11 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 Zermatt TL3/ SR3 6mm ARC Threaded Rifle Barrel: Manufacturer: Proof Research Caliber: 6mm ARC Barrel Twist Rate: 1-7.5 Firearms Threads Per Inch: 5/8x24 Gun Make: Zermatt Arms Gun Model: Zermatt SR3 Zermatt TL3 Gun Type: Rifle Package Contents: Proof Research Zermatt TL3/ SR3 6Arc Threaded Rifle Barrel What firearm models does the manufacturer say Proof Research Zermatt TL3/ SR3 6mm ARC Threaded Rifle Barrel is compatible with? The manufacturer suggests that Proof Research Zermatt TL3/ SR3 6mm ARC Threaded Rifle Barrel is compatible with Zermatt TL3 Zermatt SR3Proof Research 157237: Zermatt TL3/ SR3 6mm ARC Threaded Rifle Barrel Sendero 20 in 7.5 Twist Pxt 5/8-24 Thread 2.11 Weight Carbon