CVA Accura MR-X with 3/4 x 24 Threaded Barrel 50 Caliber Sniper Gray Cerakote/Veil Apline SingleShot Muzzleloader - 26in - The ACCURA MR-X is our shorter-barreled ACCURA muzzleloader (the MR stands for Mountain Rifle) and features a 26in Bergara barrel. The MR-X is designed for hunters seeking a rifle that is both light to carry in the mountains and easy to maneuver in tight situations, like thickets or tree stands, yet still capable of reaching out there when necessary.