JP Enterprises Enhanced Bolt/Carrier 9mm Black. In fact when combined with our JPSCS-9MM you have the heaviest most reliable 9mm operating system that dramatically reduces bolt bounce while improving accuracy. This bolt assembly is .9 oz. heavier than the Rock River Arms 9mm bolt with its central mass removed. When used in conjunction with the Silent Captured Spring the complete JP 9mm operating system is slightly heavier than the complete RRA bolt and buffer some of the bolt mass having been transferred to the SCS in our system. Specifications for JP Enterprises Enhanced Bolt/Carrier 9mm: Manufacturer: JP Enterprises Caliber: 9mm Luger Features of JP Enterprises Enhanced Bolt/Carrier 9mm: Reduced stroke length for faster firing impulse when used with JPSCS-9MM. Designed for optimal function with JPSCS-9MM for a heavier operating system that reduces bolt bounce while improving reliability and accuracy. Tighter firing pin channel to reduce pin wear. High-energy tumble process offers a finer cosmetic finish. Includes firing pin and retainer pin. Package Contents: JP Enterprises Enhanced Bolt/Carrier 9mm JP Enterprises JPBC-9MMA: Enhanced Bolt/Carrier 9mm Black