Primary Weapons Systems MK109 MOD 1-M 300BLK Upper 9.75" - MK1-M1U-300BLK-9

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Primary Weapons Systems® MK109 MOD 1-M Complete Upper Receiver Assembly – Fits Standard AR-15 Lowers – .300 AAC Blackout – 9.75" Match Grade Barrel – Iconic Long-Stroke Piston System – Matte Black Anodized – MK1-M1U-300BLK-9

Product Description

The Primary Weapons Systems® MK109 MOD 1-M Complete Upper Receiver Assembly (MK1-M1U-300BLK-9) represents a world-class pinnacle in short-barrel operational physics and suppressed AR-15 weapon staging, masterfully engineered in Boise, Idaho to deliver flawless cycling authority under intense field conditions. Unlike standard short-barreled rifles (SBR) and pistol builds that rely on a traditional direct impingement (DI) gas tube—which continuously blasts hot, corrosive carbon fouling and abrasive blowback directly into the bolt carrier group and receiver cavity—PWS completely re-engineers the platform. Utilizing their highly decorated, combat-proven long-stroke piston operating system, this complete upper physically links the gas piston face and operating rod directly to the bolt carrier matrix as a single cohesive reciprocating mass. This layout isolates the internal mechanics from exhausting gases, ensuring your upper runs dramatically cleaner, cooler, and with an elite level of structural reliability that mimics the legendary mechanics of the AK-47 platform inside a precision American AR envelope.

The core structural and barrel architecture of this premium 300 Blackout powerhouse (811154033451) is meticulously tuned to exploit the native terminal ballistics of the 7.62x35mm cartridge. Featuring a 9.75" precision-crafted 41V50 chrome moly vanadium steel barrel optimized with a rapid 1:8" stabilization twist rate, the system handles heavy subsonic loads up to 220 grains and high-velocity supersonic defensive cartridges with equal sub-MOA precision. While a short 5.56 NATO barrel wastes an immense portion of its powder charge into an obnoxious, blinding fireblast outside the muzzle, the .300 BLK propellant finishes complete combustion within this compact 9.75-inch envelope. The barrel is housed within a fully forged, heavy-walled 7075-T6 aerospace aluminum upper receiver shell treated with a low-friction, scratch-defying Mil-Spec Type III Matte Black hardcoat anodized armor finish, preserving tight spatial alignment bounds across extensive training cycles.

The true operational triumph of this American-built tactical masterwork lies in its suppressor-optimized ergonomics and complete, drop-in build fulfillment. Surrounding the piston drive train is an 8.9" free-floating M-LOK handguard that provides an unyielding, rigid mounting layout for weapon lights, lasers, and barrier stops while keeping your support hand perfectly shielded from thermal transfer. PWS finishes the muzzle with a PWS Triad 30 muzzle compensator / FRC architecture on standard 5/8"-24 threads, controlling muzzle rise while remaining fully compatible with modern suppressor mounting interfaces. Fully assembled and ready to pin directly onto any standard Mil-Spec AR-15 lower receiver, this premium 3.50-pound upper comes outfitted from the factory with a specialized PWS long-stroke bolt carrier group and a premium Radian Raptor™ ambidextrous charging handle, granting you total mechanical authority and zero-fail staging on the active firing line.

Includes: (1) PWS MK109 MOD 1-M Complete Upper Receiver Assembly (Black Anodized, 9.75" Barrel, Piston Operating Train), (1) Pre-Installed PWS Long-Stroke Bolt Carrier Group (BCG), (1) Radian Raptor Ambidextrous Charging Handle, (1) Pre-Timed Triad 30/FRC Muzzle Device, and Factory Branded Cardboard Protective Storage Transport Boxing.

*Safety/Installation & Regulatory NFA Guidance: The PWS MK1-M1U-300BLK-9 complete upper receiver is designed to instantly pin onto any standard, mil-spec AR-15 lower receiver assembly. Because this unit incorporates a 9.75-inch short barrel, installing it onto a lower receiver natively configured with a standard rifle buttstock reclassifies the firearm as a Short Barreled Rifle (SBR) under federal jurisdiction, requiring active National Firearms Act (NFA) registration and an approved ATF Form 1 prior to assembly. To maintain lawful civilian compliance without NFA paperwork, ensure this upper is hosted exclusively on an AR-15 lower receiver legally registered and maintained as a handgun/pistol configuration. Always confirm your firearm is completely unloaded and physically clear prior to running assembly pin alignments.

Key Features

• Elite Long-Stroke Piston System: Combines the cleaning ease and severe-duty reliability of an AK platform with the high ergonomics and custom modularity of the AR-15.
• Optimized Suppressor Performance: Dramatically slashes high backpressure gas blowback into the shooter’s face, delivering a significantly more comfortable suppressed tracking string.
• Match-Grade 9.75" 41V50 Barrel: High-yield chrome-moly-vanadium barrel with a 1:8 twist stabilizes a vast spectrum of subsonic and supersonic .300 Blackout ammunition.
• Radian Raptor™ Charging Handle: Factory-equipped with a premium ambidextrous charging handle to ensure smooth, high-traction manual rack cycles from either side of the chassis.
• Monolithic 8.9" Free-Float M-LOK: Lightweight, ultra-slim structural handguard provides extensive accessory placement real estate without contacting or deflecting barrel harmonics.
• Fully Forged 7075-T6 Receiver: Mil-Spec forged aluminum upper receiver provides high shear strength and absolute structural stability over thousands of rapid cyclic loops.

Product Specifications

• Brand: Primary Weapons Systems® / PWS (Boise, Idaho, USA)
• Product Line: MK1 MOD 1-M Military-Grade Long-Stroke Piston Series
• Model Series Designation: PWS MK109 MOD 1-M Complete Upper Receiver Assembly
• SKU / MPN: MK1-M1U-300BLK-9 (Alternative Factory Identifiers: MK1M1U300BLK9 / M109UB01-1F)
• Firearm Lower Compatibility: Fits All Standard Mil-Spec AR-15 Lower Receivers (Handgun or Registered SBR Layouts)
• Caliber Class Chambering: .300 AAC Blackout (7.62x35mm / 300 BLK)
• Operating System Layout: Proprietary PWS Long-Stroke Piston Drive Core (Non-Adjustable Fixed Gas Port Loop)
• Barrel Length Specification: 9.75 Inches (247.65 mm) Short-Barrel Ballistic Baseline
• Barrel Material Matrix: 41V50 Chrome Moly Vanadium Steel Core with Button Rifling
• Rifling Twist Rate Parameter: 1:8" Right-Hand Precision Twist (Optimized for Subsonic Heavy Matrix Loads)
• Muzzle Thread Footprint: 5/8"-24 TPI (Threads Per Inch) Standard Heavy Caliber Profile
• Muzzle Device Component: PWS Triad 30 Flash Hider Compensator / Suppressor Compatible Anchor
• Handguard Attachment Class: 8.9-Inch PWS Free-Float M-LOK Modular Attachment Rail Shield
• Upper Receiver Shell Base: Forged 7075-T651 Aircraft Structural Aluminum Block
• Surface Finishing Armor: Low-Glare Mil-Spec Type III Hardcoat Matte Black Anodization
• Bolt Carrier Group Core: PWS Proprietary Long-Stroke Piston BCG (Piston Head Integrated to Carrier)
• Charging Handle Interface: Included Radian Raptor™ Dual-Wing Ambidextrous Operating Handle
• Product Net Component Weight: ~3.50 lbs (~56.00 oz) - Low-Mass Agile Compact Upper Deck
• Total Packaging Shipping Mass: ~4.75 lbs (Enclosed Inside Heavy Padded Protective Distribution Boxing)
• UPC Barcode: 811154033451