AR-15 MK1 Mod 1-M Upper Receiver Assembly 300 Blackout M-LOK - MK109 Mod 1-M 300BLK Upper Receiver W/9.75" Bbl
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Primary Weapon Systems
Overview
The Primary Weapon Systems AR-15 Mk1 Mod 1-M Upper Receiver Assembly is a complete setup designed for the 300 Blackout caliber, featuring a 9.75-inch barrel that optimizes performance for both subsonic and supersonic ammunition. This upper receiver is built on the AR-15 platform, allowing for easy integration with your existing lower receiver and ensuring compatibility with a wide range of accessories. This assembly is commonly used in builds focused on compact tactical applications and home defense, where maneuverability and effective terminal ballistics are crucial.
Specifications
AR-15 MK1 Mod 1-M Upper Receiver Assembly 300 Blackout M-LOK - MK109 Mod 1-M 300BLK Upper Receiver W/9.75" Bbl
Available Merchants(5)
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Price Alert
Build history on GunPartPicker
Builders on GunPartPicker first added the Primary Weapon Systems AR-15 MK1 Mod 1-M Upper Receiver Assembly 300 Blackout M-LOK - MK109 Mod 1-M 300BLK Upper Receiver W/9.75" Bbl to a build in July 2026.
It was in stock most days in September 2026, and today 4 of the 5 retailers we track have it in stock. It dipped to $1,049.95 at Sportsmans Outdoor Superstore for a stretch in September 2026, under its usual $1,129.95, so sales do come around. Buying today, the lowest price is $1,129.95 at Brownells, above September's low of $1,049.95, so a better deal may come back.
Updated · from real builds on GunPartPicker · Prices checked · refreshed daily across 37 retailers
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