JP Low Mass Operating System Bolt Carrier Large-Frame (.308) Stainless Steel Polished Finish Requires DPMS-pattern bolt, firing pin, firing pin retainer pin and cam pin. Weight: 10.82 oz. with key installed. Compatibility This notice pertains to any rifle based on the large-format AR-10-type or LR-308 platform typically chambered in .308 Winchester, 7.62x51 NATO or other cartridges requiring the longer magazine format. Be aware that these receiver platforms are not standardized like the AR-15/M16 platform for which most parts are cross-compatible. Before ordering accessories and parts for your large-format rifle, make sure the parts are compatible with your particular platform. This bolt carrier is compatible only with the DPMS family of AR-10 products. With the Armalite family of large-frame receivers, this carrier can only be used as a complete bolt carrier assembly group with a DPMS-pattern bolt such as our .308 JP EnhancedBolt. Interchanging individual components will result in an unsafe configuration. Do Not under any circumstances mix and match components between the platforms.