Cycling Problems? The VMOS™ brings the discipline your rifle needs.

For difficult setups like suppressed rifles and exotic caliber chamberings, some degree of mass regulation is required for optimal performance. This is especially true in the absence of an adjustable gas block. Residual gas and excessive fouling can grind your rifle to a stop.

One size never fits all when it comes to gas-operated rifles. The Variable Mass Operating System (VMOS™) carrier ensures reliability through additional reciprocating mass but provides more custom tunability. Combined with our Silent Captured Spring, multiple masses are exchangeable to perfectly tune your operating system weight. This standard version of the large-frame VMOS™ carrier includes three steel weights, two of which can be exchanged for heavier tungsten weights.

Package includes carrier, JP Enhanced Gas Ring and instruction sheet.

Features:

• Enhanced tunability of operating system
• Guaranteed reliability of difficult configurations
• Overcomes all fouling build-up
• Roller-burnished bore for frictionless operation
• Rock-hard QPQ finish provides remarkable natural lubricity
• Extremely smooth cycling with proper lubrication
• Increased bearing surfaces for slower wear and longer component life
• Longer cocking pad for optimal reliability
• American made

Kit includes bolt assembly, firing pin, cam pin and retainer pin. This version of the bolt is compatible with the JP LRP-07 and the DPMS LR-308 platforms (or clones thereof) only and cannot be used to replace bolts in the Armalite AR-10 platform (or clones thereof).

• Allows reliable AR functional with previously incompatible over-pressured loads such as 6.5mm or 6mm calibers
• Virtually eliminates primer flow and pierced primers
• Reduced firing pin mass improves lock time and ignition reliability with hard primers
• Features same quality construction and advantages of other JP EnhancedBolts™
• Backwards compatible with standard .308 ejectors, extractors and gas rings
• Lifetime bolt warranty

Specifications:

• Caliber: .308 Win.
• Finish: Chromium Nitride
• Weight: 1 lbs 3.7 oz.

Compatibility:

• The large-frame VMOS™ carrier uses the same steel and tungsten weights as GEN 2 Silent Captured Spring units. Only the forward two masses are reconfigurable. The rear-most steel mass cannot be exchanged.
• This carrier will not cycle with a standard buffer retainer plunger installed. Standard buffer/spring components must be installed “loose” or replaced with a Silent Captured Spring.

Please NOTE: 

• 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/Rock River 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.