SIG Sauer MCX .177 Cal CO2 Powered Advanced Air Rifle with CO2 90 Gram (2 Pack) and 500 Lead Pellets Bundle (FDE, 1-4x24 Scope). From tactical drills to target practice, the CO2 powered SIG MCX Air Rifle delivers 30 rounds of rapid-firing, simulated SIG MCX performance and handling for more realistic, economical training and practice — any time, any place. Chambered in .177 pellet, features include an 18" rifled steel barrel, synthetic handguard, picatinny rail, tactical front grip, flip-up front and rear sights and more.