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Primary Weapons Systems
The Primary Weapons Systems MK109 MOD 1-M upper receiver brings PWS's proven long-stroke piston system to the 300 Blackout platform in a compact 9.75-inch configuration. Built for shooters who want precision, reliability, and flexibility in a short-barreled rifle setup, this complete upper combines PWS's reputation for clean, low-fouling operation with thoughtful features for both supersonic and subsonic ammunition. Whether you're running suppressed or unsuppressed, hunting, or running drills at distance, the MK109 MOD 1-M is engineered to handle it.
The heart of this upper is PWS's long-stroke piston system, which cycles reliably across diverse ammunition loads and environmental conditions while keeping the bolt carrier group cleaner than direct-impingement designs. The 3-setting adjustable gas block lets you dial in the exact amount of backpressure for your ammunition, suppressor setup, and shooting environment—a critical advantage when you're tuning a short-barreled 300 BLK upper. The Triad 30 muzzle device mitigates recoil and muzzle rise, maintaining your sight picture and control through rapid strings or follow-up shots.
The integrated PicLok handguard merges Picatinny rail and M-LOK slots in a single platform, giving you mounting versatility without compromising ergonomics or adding bulk. At 9.75 inches, the barrel length keeps the overall package compact while delivering the velocity and accuracy 300 BLK demands—especially valuable if you're running a suppressor and want to keep subsonic loads subsonic without sacrificing sight radius or balance.
PWS barrels are manufactured in Boise and held to tight tolerances for accuracy. This upper comes ready to bolt onto any standard AR-15 lower receiver, so you can have your 300 BLK short-barreled rifle up and running without piecing together parts from multiple vendors.
| Brand | Primary Weapons Systems |
| Model | MK109 MOD 1-M |
| Caliber | 300 Blackout |
| Barrel Length | 9.75 inches |
| Gas System | Long-stroke piston, 3-setting adjustable |
| Muzzle Device | PWS Triad 30 |
| Handguard | PicLok (Picatinny and M-LOK compatible) |
| Type | Complete upper receiver |
Yes, the MK109 MOD 1-M is a complete upper receiver that attaches to any standard AR-15 lower receiver via the upper receiver pin holes.
Yes, the MK109 MOD 1-M is designed to work with both supersonic and subsonic 300 Blackout loads. The 3-setting adjustable gas block allows you to dial in the proper gas flow for your chosen ammunition type.
Yes, the adjustable gas system is designed to be suppressor-friendly, allowing you to minimize backpressure and optimize gas flow when running a suppressor.
The MK109 MOD 1-M comes equipped with the PWS Triad 30 muzzle device, which is designed to reduce recoil and muzzle rise for better shooter control.
Primary Weapons Systems
The Primary Weapons Systems MK109 MOD 1-M upper receiver brings PWS's proven long-stroke piston system to the 300 Blackout platform in a compact 9.75-inch configuration. Built for shooters who want precision, reliability, and flexibility in a short-barreled rifle setup, this complete upper combines PWS's reputation for clean, low-fouling operation with thoughtful features for both supersonic and subsonic ammunition. Whether you're running suppressed or unsuppressed, hunting, or running drills at distance, the MK109 MOD 1-M is engineered to handle it.
The heart of this upper is PWS's long-stroke piston system, which cycles reliably across diverse ammunition loads and environmental conditions while keeping the bolt carrier group cleaner than direct-impingement designs. The 3-setting adjustable gas block lets you dial in the exact amount of backpressure for your ammunition, suppressor setup, and shooting environment—a critical advantage when you're tuning a short-barreled 300 BLK upper. The Triad 30 muzzle device mitigates recoil and muzzle rise, maintaining your sight picture and control through rapid strings or follow-up shots.
The integrated PicLok handguard merges Picatinny rail and M-LOK slots in a single platform, giving you mounting versatility without compromising ergonomics or adding bulk. At 9.75 inches, the barrel length keeps the overall package compact while delivering the velocity and accuracy 300 BLK demands—especially valuable if you're running a suppressor and want to keep subsonic loads subsonic without sacrificing sight radius or balance.
PWS barrels are manufactured in Boise and held to tight tolerances for accuracy. This upper comes ready to bolt onto any standard AR-15 lower receiver, so you can have your 300 BLK short-barreled rifle up and running without piecing together parts from multiple vendors.
| Brand | Primary Weapons Systems |
| Model | MK109 MOD 1-M |
| Caliber | 300 Blackout |
| Barrel Length | 9.75 inches |
| Gas System | Long-stroke piston, 3-setting adjustable |
| Muzzle Device | PWS Triad 30 |
| Handguard | PicLok (Picatinny and M-LOK compatible) |
| Type | Complete upper receiver |
Yes, the MK109 MOD 1-M is a complete upper receiver that attaches to any standard AR-15 lower receiver via the upper receiver pin holes.
Yes, the MK109 MOD 1-M is designed to work with both supersonic and subsonic 300 Blackout loads. The 3-setting adjustable gas block allows you to dial in the proper gas flow for your chosen ammunition type.
Yes, the adjustable gas system is designed to be suppressor-friendly, allowing you to minimize backpressure and optimize gas flow when running a suppressor.
The MK109 MOD 1-M comes equipped with the PWS Triad 30 muzzle device, which is designed to reduce recoil and muzzle rise for better shooter control.
