Davidson Defense Afterstate w/SBA5 Brace 10.5-inch Pistol-Gas 1:8 .300 BLK AR-15 FSB Carbine-Length Quad-Rail Handguard Pistol Full Build Kit

Davidson Defense Afterstate w/ SBA5 Brace 10.5" .300 BLK AR-15 Pistol Full Build Kit | Pistol-Gas | 1:8 Twist | 4150 CrMoV Nitride Barrel | Quad-Rail | Adjustable Stabilizing Brace

A versatile .300 Blackout full build kit with SB Tactical SBA5 adjustable stabilizing brace for modern ergonomics and length-of-pull customization. Built around a 10.5-inch 4150 CrMoV nitride barrel with 1:8 twist rate, this configuration stabilizes bullet weights from 110 to 220 grains across subsonic and supersonic loads. The pistol-length gas system features a dedicated gas block mounted beneath the handguard, ensuring reliable cycling and manageable recoil characteristics. The 7-inch carbine-length quad-rail handguard machined from 6061-T6 aluminum provides extensive four-sided Picatinny rail coverage for lights, optics, and accessories while maintaining a lightweight profile. This full build kit includes a complete 9310 alloy steel bolt carrier group, mil-spec charging handle, mil-spec heavy-duty buffer tube assembly, and the adjustable SB Tactical SBA5 pistol stabilizing brace for enhanced shooting stability across multiple shooter sizes and preferences.

Key Features

• 10.5" 4150 CrMoV Nitride Barrel: 1:8 twist rate stabilizes .300 BLK bullet weights from 110 to 220 grains
• SB Tactical SBA5 Adjustable Pistol Stabilizing Brace: Multiple positions of length-of-pull adjustment with modern ergonomics and enhanced shooting stability
• Complete 9310 Alloy Steel Bolt Carrier Group: Wear resistance and consistent cycling across varied ammunition types
• Mil-Spec Heavy-Duty Buffer Tube Assembly: Reliable recoil management and robust component durability
• Pistol-Length Gas System: Dedicated gas block mounted under handguard—optimized dwell time and pressure regulation for reliable .300 Blackout function
• 7" Carbine-Length Quad-Rail Handguard: 6061-T6 aluminum construction with continuous four-sided Picatinny rail coverage
• 7075-T6 Aluminum Upper Receiver: Anodized finish provides durability and corrosion resistance
• Mil-Spec Charging Handle: Standard AR-15 reciprocating operation and compatibility

Perfect For

• .300 Blackout AR-15 pistol builds requiring complete component packages with adjustable SBA5 brace
• Home defense and vehicle-based applications demanding compact, maneuverable platforms
• Shooters who value length-of-pull adjustability and modern brace design for enhanced control
• Builders seeking a comprehensive kit with proven SBA5 brace, BCG, buffer assembly, and charging handle
• Range and tactical environments where both subsonic and supersonic .300 BLK loads are employed

Complete Pistol Build Package with SBA5 Adjustability

This full build kit includes all essential upper, buffer, and brace components for completing an AR-15 pistol build. The included 9310 alloy steel bolt carrier group provides reliable extraction and ejection across varying ammunition types, while the mil-spec charging handle ensures standard reciprocating operation. The mil-spec heavy-duty buffer tube assembly delivers robust recoil management and provides the mounting foundation for the SB Tactical SBA5 adjustable pistol stabilizing brace. The SBA5 offers multiple positions of length-of-pull adjustment, allowing shooters to optimize fit for different shooting stances, gear loadouts, or individual preferences while enhancing control and maintaining consistent sight alignment during rapid-fire strings. See configuration for lower receiver options to complete your build.

Optimized .300 BLK Barrel Configuration

The 10.5-inch barrel length maximizes powder burn efficiency for .300 Blackout chambering while maintaining a compact, maneuverable profile. The 1:8 twist rate stabilizes bullet weights ranging from 110 to 220 grains, accommodating both high-velocity supersonic loads and quiet subsonic expansion rounds. The 4150 CrMoV steel construction with nitride finish delivers superior corrosion resistance, enhanced surface hardness, and bore protection, extending barrel life even in harsh environmental conditions while reducing friction for smooth cycling performance.

Pistol-Length Gas System and Buffer Assembly

The pistol-length gas system is purpose-built for short-barreled .300 Blackout configurations, featuring a dedicated gas block positioned beneath the handguard—not integrated with a front sight base. This setup provides optimal dwell time and pressure regulation, ensuring consistent cycling across the full spectrum of .300 BLK ammunition—from light supersonic loads to heavy subsonic projectiles—while managing felt recoil and maintaining ejection reliability. The included mil-spec heavy-duty buffer tube assembly works in tandem with the gas system to provide dependable recoil management and serves as the structural foundation for the SBA5 brace, ensuring secure attachment and consistent performance under dynamic shooting conditions.

Quad-Rail Modularity and SBA5 Stability

The 7-inch carbine-length quad-rail handguard delivers continuous Picatinny rail coverage on all four sides, accommodating weapon lights, laser aiming devices, vertical grips, and optic risers. Machined from 6061-T6 aluminum, the handguard maintains structural rigidity under recoil while keeping overall weight manageable. The included SB Tactical SBA5 adjustable brace complements the quad-rail's versatility by providing a stable, customizable shooting platform with modern ergonomics that enhance control during target transitions and follow-up shots, making this kit well-suited for dynamic shooting applications across multiple shooter sizes and preferences.

Follow safe handling practices and manufacturer instructions at all times. Ensure compliance with all applicable federal, state, and local laws. Verify .300 BLK ammunition compatibility and avoid mixing calibers. Confirm proper headspacing and component fitment before firing.