Aero Precision M4E1 Threaded Barreled AR-15 Upper Receiver .300 Black Pistol - Atlas R-One - 10"
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Aero Precision
Overview
The Aero Precision M4E1 Threaded Barreled AR-15 Upper Receiver in .300 Blackout is a complete assembly designed specifically for pistol builds. With a 10-inch barrel length and a 1:7 twist rate, it effectively stabilizes heavier projectiles, making it ideal for a variety of ammunition types. The pistol-length gas system ensures reliable cycling in compact configurations, while the 5/8x24 thread pitch allows for compatibility with a range of muzzle devices. This upper is commonly found in builds focused on .300 Blackout, particularly those emphasizing maneuverability and versatility.
Specifications
Aero Precision M4E1 Threaded Barreled AR-15 Upper Receiver .300 Black Pistol - Atlas R-One - 10"
Available Merchants(5)
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September 2026 on GunPartPicker
Aero Precision M4E1 Threaded Barreled AR-15 Upper Receiver .300 Black Pistol - Atlas R-One - 10" ranked #267 of the 615 upper receivers builders added on GunPartPicker in September 2026. Builders have been adding it to their builds on GunPartPicker since February 2026. All time, it ranks #143 of the 1,654 upper receivers builders have added. Builds with this upper receiver are nearly all chambered in 300 Blackout, nearly all on pistol-length gas, and nearly all AR-15.
It was out of stock everywhere we track for all of September 2026, and today none of the 5 retailers we track has it in stock right now. Listed prices start at $510.99 at KY Gun Company for when it comes back.
Updated · from real builds on GunPartPicker · Prices checked · refreshed daily across 35 retailers
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