PWS MK109 MOD 1 Upper Receiver - 300 BLK, 9.75" Barrel, TRIAD30 Muzzle DevicePrimary Weapons Systems$1,029.49
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Primary Weapons Systems
The PWS MK109 MOD 2-M is a complete 300BLK upper receiver built for shooters who demand proven piston-driven reliability in a compact, versatile platform. Primary Weapons Systems engineered this 9.75" upper around their long-stroke piston operating system—a design choice that separates it from the direct impingement crowd. Whether you're running subsonic loads through a suppressor, hunting with supersonic ammunition, or putting rounds downrange at the bench, the adjustable gas regulator lets you dial in your specific load and configuration for clean, consistent cycling.
The MK109 MOD 2-M arrives complete and ready to pair with a compatible lower receiver. You get a PWS proprietary piston upper receiver finished in hard coat anodize per Mil-Spec 8625, an 8.9" PWS PicLok handguard sized for comfortable control and mounting flexibility, and a Radian Raptor ambidextrous charging handle that works equally well for lefties and right-handers. The 1:8 twist rate and 9.75" barrel are optimized for 300BLK performance across the velocity spectrum, and the PWS Triad 30 muzzle device is already installed—no guessing about muzzle rise or blast direction.
This is a solid choice for 300BLK shooters who value the inherent advantages of a piston system: less carrier tilt, easier cleaning cycles, and the ability to run suppressed or unsuppressed without major adjustments. If you're building a versatile AR pistol or short-barreled rifle in 300 Blackout, the MK109 MOD 2-M gives you quality engineering and real-world performance without reinventing the wheel.
| Caliber | .300 AAC Blackout (300BLK) |
| Barrel Length | 9.75" |
| Barrel Twist Rate | 1:8 |
| Gas System | Pistol-length piston |
| Operating System | PWS long-stroke piston with 3-setting adjustable gas regulator |
| Upper Receiver | PWS proprietary piston upper, 7075-T651 aluminum, hard coat anodized per Mil-Spec 8625 Type III Class 2 |
| Handguard | PWS PicLok, 8.9" length, 1.7" width, 2.25" height |
| Charging Handle | Radian Raptor ambidextrous |
| Muzzle Device | PWS Triad 30 (installed) |
| Muzzle Velocity | 2,264 fps |
The MK109 MOD 2-M's adjustable piston regulator lets you tune gas flow to work cleanly with or without a suppressor. For suppressed fire, you can dial back the regulator to reduce bolt velocity and mitigate excess backpressure—a major advantage of the piston system over direct impingement designs.
The MK109 MOD 2-M is a complete upper receiver compatible with any standard AR-15 lower receiver. No special tooling or adapters are required beyond a basic roll pin or multi-tool to install the barrel extension pin.
The Triad 30 comes installed on the barrel. Whether it's user-removable depends on how it's attached (pinned, timed, or threaded). Contact Bosque or consult the manual for details on removal and re-timing if needed.
The 1:8 twist rate and 9.75" barrel handle both subsonic (below 1,125 fps) and supersonic (above 1,125 fps) 300BLK ammunition. The adjustable gas regulator helps optimize performance across different load weights and velocities.
Primary Weapons Systems
The PWS MK109 MOD 2-M is a complete 300BLK upper receiver built for shooters who demand proven piston-driven reliability in a compact, versatile platform. Primary Weapons Systems engineered this 9.75" upper around their long-stroke piston operating system—a design choice that separates it from the direct impingement crowd. Whether you're running subsonic loads through a suppressor, hunting with supersonic ammunition, or putting rounds downrange at the bench, the adjustable gas regulator lets you dial in your specific load and configuration for clean, consistent cycling.
The MK109 MOD 2-M arrives complete and ready to pair with a compatible lower receiver. You get a PWS proprietary piston upper receiver finished in hard coat anodize per Mil-Spec 8625, an 8.9" PWS PicLok handguard sized for comfortable control and mounting flexibility, and a Radian Raptor ambidextrous charging handle that works equally well for lefties and right-handers. The 1:8 twist rate and 9.75" barrel are optimized for 300BLK performance across the velocity spectrum, and the PWS Triad 30 muzzle device is already installed—no guessing about muzzle rise or blast direction.
This is a solid choice for 300BLK shooters who value the inherent advantages of a piston system: less carrier tilt, easier cleaning cycles, and the ability to run suppressed or unsuppressed without major adjustments. If you're building a versatile AR pistol or short-barreled rifle in 300 Blackout, the MK109 MOD 2-M gives you quality engineering and real-world performance without reinventing the wheel.
| Caliber | .300 AAC Blackout (300BLK) |
| Barrel Length | 9.75" |
| Barrel Twist Rate | 1:8 |
| Gas System | Pistol-length piston |
| Operating System | PWS long-stroke piston with 3-setting adjustable gas regulator |
| Upper Receiver | PWS proprietary piston upper, 7075-T651 aluminum, hard coat anodized per Mil-Spec 8625 Type III Class 2 |
| Handguard | PWS PicLok, 8.9" length, 1.7" width, 2.25" height |
| Charging Handle | Radian Raptor ambidextrous |
| Muzzle Device | PWS Triad 30 (installed) |
| Muzzle Velocity | 2,264 fps |
The MK109 MOD 2-M's adjustable piston regulator lets you tune gas flow to work cleanly with or without a suppressor. For suppressed fire, you can dial back the regulator to reduce bolt velocity and mitigate excess backpressure—a major advantage of the piston system over direct impingement designs.
The MK109 MOD 2-M is a complete upper receiver compatible with any standard AR-15 lower receiver. No special tooling or adapters are required beyond a basic roll pin or multi-tool to install the barrel extension pin.
The Triad 30 comes installed on the barrel. Whether it's user-removable depends on how it's attached (pinned, timed, or threaded). Contact Bosque or consult the manual for details on removal and re-timing if needed.
The 1:8 twist rate and 9.75" barrel handle both subsonic (below 1,125 fps) and supersonic (above 1,125 fps) 300BLK ammunition. The adjustable gas regulator helps optimize performance across different load weights and velocities.
