The CAR816 A2 is chambered in 5.56x45mm NATO. The short-stroke push rod gas piston design is controlled by a three-position gas valve. It's manufactured with the best materials such as a Carpenter 158 bolt housed in an anti-tilt carrier, 4150 CMV barrel and aircraft-grade aluminum. These materials, when partnered with our unique barrel extension and chamber design, give exceptional accuracy as well as the ability to surpass NATO testing protocols, including destructive testing. Proudly manufactured in the United States. * 5.56x45mm NATO Gas Operated Short Stroke Piston with 3 Position Adjustable gas key * Built to exceed NATO test protocols; Bore Obstruction and "Over the Beach" Testing. * Forged 7075 Hard Coat Anodized upper and lower receiver set * 9 Handguard with key lock anti-cant, integrated QD points and Mlok attachment system * QPQ 4150 CMV Barrel with Caracal Barrel Extension and Chamber Design * QPQ BCG, Caracal Anti Tilt Carrier with Carpenter 158 Bolt. * Enhanced Duty Trigger, Ambi Selector, and stakeless end plate with integrated QD point. * Lifetime Warranty