Purpose-built for 9mm AR-15 pistol caliber carbines, their Generation 2 PCC blow-back carriers keep the features of their well-loved first BCG with modern improvements. They maintain the dual COLT/GLOCK compatible geometry, user-removable weight and full-auto compatibility while adding new and welcome features. They maintain a ramped bottom so any common trigger can be used - ideal for competitive shooters and plinkers alike. The extractor has been upgraded to an AR-15 pivoted and sprung option. For ease of disassembly, a standard firing pin cotter pin is used, and to ensure long-life, the carrier key is separate from the charging surface ensuring that the carrier stands up to any vigorous action - no sheared keys! A stronger firing pin rounds out the new changes.