JP LMOS™ 308 Carrier Group with High Pressure JP EnhancedBolt™ Stainless Steel QPQ Black Finish

Complete bolt carrier assembly with JPBC-4 stainless .308 Low Mass Carrier and JPEB-308HP JP High Pressure EnhancedBolt™, cam pin, firing pin and firing pin retainer.

JP Low Mass Operating System

For the no-compromise competition rifle, our Low Mass Operating System (LMOS™) offers the most significant improvement in the felt impulse of the rifle compared to any modification other than the addition of a compensator. By reducing the reciprocating mass within the operating system, the bolt velocity is increased while simultaneously reducing the overall impulse experienced by the shooter with each shot. Consequently, LMOS™ equipped rifles have virtually no reciprocating mass feel and move less during cycling, allowing for much faster sight recovery and follow-up shots.

While use of the LMOS™ components is recommended only for competition and sporting use, this is only precautionary as their reliability is excellent, particularly on rifles with adjustable gas systems. Like all our bolt carrier designs, LMOS™ carriers feature a 100% increase in bearing surface for smoother operation, improved alignment and lower wear in the upper receiver as well as the longer Mil-spec. cocking pad for optimal reliability. In fact, Team JP shooters have been using the LMOS™ system for over a decade without any reported operating system malfunctions at a match, and most every shooter that implements this operating system feel that it is proven to be a great performance improvement. Some shooters have even reported fewer unexplained flyers in their groups after switching to the LMOS™ system.

WARNING: The JP .308HP bolt does not allow for the use of excessive pressure, overloaded ammunition that exceeds SAAMI specifications. When evaluating new ammunition, always start on the low- to mid-range of any published load data and work up. A good indicator of working pressure is the primer retention on the subsequent loading of a case. A noticeable loss of primer pocket tension indicates that your ammunition has excessive pressure and has overworked the case.

BC-4 Bolt Carrier Assembly Group AR-10 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. The JPBC-4AHP complete bolt carrier assembly and its parts are compatible with the DPMS family of AR-10 products. 

NOTICE: With the Armalite/Rock River family of large-frame receivers, this assembly can only be used as a complete bolt carrier assembly group. Interchanging individual components will result in an unsafe configuration. DO NOT under any circumstances mix and match components between the platforms. Only use the complete JP bolt carrier assembly in the Armalite/Rock River platforms.