Radical Firearms 300 Blackout 8.5" Upper Receiver Assembly Black RF00351 (UPC 816903024063)

The Radical Firearms 300 Blackout 8.5" Upper Receiver Assembly Black RF00351 (UPC 816903024063) is a compact, high-performance complete upper designed for builders looking to create a short-barreled .300 Blackout AR-15 pistol or SBR. Manufactured by Radical Firearms, this 8.5-inch upper combines the versatility of the 300 BLK cartridge with an ultra-compact barrel length, making it an excellent choice for home defense, suppressed shooting, and close-quarters applications. The durable black finish provides a professional appearance while offering solid protection against wear and corrosion.

Radical Firearms has built a strong reputation for delivering reliable and affordable AR-15 components. The RF00351 upper gives builders a ready-to-install solution in one of the most popular short-barrel calibers available today.

Optimized 8.5-Inch Barrel for .300 Blackout

The 8.5-inch barrel on this Radical Firearms upper is specifically well-suited for the .300 Blackout cartridge. Unlike 5.56 NATO, .300 Blackout was designed to perform exceptionally well in short barrels. The 8.5" length allows the cartridge to achieve optimal velocity and terminal performance while keeping the overall firearm extremely compact and maneuverable. This makes the RF00351 an outstanding choice for AR-15 pistols and short-barreled rifles where maximum maneuverability is required without sacrificing effectiveness.

Complete Upper Receiver Assembly

This Radical Firearms upper comes as a complete, ready-to-install assembly. It includes the barrel, bolt carrier group, charging handle, and handguard, ensuring all components are properly matched for reliable function. The complete assembly design saves builders time and removes compatibility concerns. The upper receiver is machined to tight tolerances and works seamlessly with standard mil-spec AR-15 lower receivers, giving users the freedom to create a custom firearm tailored to their specific needs.

Ideal for Suppressed and Close-Quarters Use

The .300 Blackout cartridge paired with an 8.5-inch barrel is one of the most popular combinations for suppressed firearms. The short barrel allows subsonic ammunition to perform effectively while reducing overall length, making it easier to maneuver when using a suppressor. This upper is an excellent foundation for building a dedicated suppressed AR pistol or SBR for home defense, tactical training, or recreational shooting.

Versatile Platform for Custom Builds

The RF00351 is a popular choice among builders creating compact .300 Blackout firearms. Its short overall length makes it well-suited for home defense setups, vehicle guns, and any situation where a highly maneuverable firearm is desired. The black finish provides a clean, professional look and helps protect the components during regular use. Because it is built on the standard AR-15 platform, this upper is compatible with a wide range of aftermarket parts and accessories.

Ideal Applications

• AR-15 pistol builds in .300 Blackout
• Short-barreled rifle (SBR) configurations
• Suppressed firearm builds
• Home defense and personal protection
• Close-quarters and tactical training
• Vehicle defense and truck guns
• Custom compact .300 BLK builds

Why Choose the Radical Firearms RF00351 Upper?

• 8.5-inch barrel optimized for .300 Blackout performance
• Complete upper assembly for easy installation
• Excellent choice for suppressed and short-barreled builds
• Durable black finish for long-term protection
• Compatible with standard AR-15 lower receivers
• Backed by Radical Firearms’ reputation for value and reliability
• Compact size with effective terminal performance

The Radical Firearms 300 Blackout 8.5" Upper Receiver Assembly Black RF00351 (UPC 816903024063) is a compact and capable upper receiver designed for builders who want a short, maneuverable .300 Blackout firearm. Featuring an 8.5-inch barrel chambered in 300 Blackout and finished in durable black, this complete upper delivers excellent performance in a highly compact package. The RF00351 is particularly well-suited for AR-15 pistol builds and short-barreled rifle configurations where maximum maneuverability is required. Radical Firearms has earned a solid reputation for producing reliable and affordable AR components, and this upper continues that tradition with its quality construction and practical design. The 8.5-inch barrel length takes full advantage of the .300 Blackout cartridge’s ability to perform effectively in short barrels, making it a popular choice for suppressed firearms and close-quarters applications. Whether you’re building a dedicated home defense pistol, a compact suppressed SBR, or a custom tactical rifle, the Radical Firearms RF00351 offers a dependable foundation. Its complete assembly includes all necessary components for straightforward installation onto a compatible lower receiver. For builders seeking a compact 8.5-inch .300 Blackout upper that combines short overall length with strong performance, the Radical Firearms RF00351 delivers excellent value and reliable function in a proven platform.

Build your next .300 Blackout AR pistol or SBR with the Radical Firearms 8.5" Upper Receiver RF00351.