Davidson Defense Afterstate w/SBA3 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/ SBA3 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 adjustable SB Tactical SBA3 stabilizing brace for length-of-pull customization. Built around a 10.5-inch 4150 CrMoV barrel with government profile and 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 micro low-profile gas block mounted beneath the handguard for reliable cycling and manageable recoil characteristics. The 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, and the adjustable SB Tactical SBA3 pistol stabilizing brace for enhanced shooting stability across multiple shooter sizes and preferences.

Key Features

• 10.5" 4150 CrMoV Barrel: Government profile with 1:8 twist rate stabilizes .300 BLK bullet weights from 110 to 220 grains
• SB Tactical SBA3 Adjustable Pistol Stabilizing Brace: Five-position length-of-pull adjustment for customized fit and enhanced shooting stability
• Complete 9310 Alloy Steel Bolt Carrier Group: Wear resistance and consistent cycling across varied ammunition types
• Pistol-Length Gas System: Micro low-profile gas block mounted under handguard—optimized dwell time and pressure regulation for reliable function
• 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
• Lightweight Design: Balances robust construction with manageable overall weight

Perfect For

• .300 Blackout AR-15 pistol builds requiring complete component packages with adjustable stabilizing brace
• Home defense and vehicle-based applications demanding compact, maneuverable platforms
• Shooters who value length-of-pull adjustability for different shooting positions and body types
• Builders seeking a comprehensive kit with proven SBA3 brace, BCG, and charging handle
• Range and tactical environments where both subsonic and supersonic .300 BLK loads are employed

Complete Pistol Build Package with SBA3 Adjustability

This full build kit includes all essential upper 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 SB Tactical SBA3 adjustable pistol stabilizing brace delivers enhanced shooting stability with five positions of length-of-pull adjustment, allowing shooters to optimize fit for different shooting stances, gear loadouts, or individual preferences. This adjustability enhances control and helps maintain 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 government profile provides durability under sustained fire without excessive weight penalty. 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 and bore protection, extending barrel life even in harsh environmental conditions.

Pistol-Length Gas System Engineering

The pistol-length gas system is purpose-built for short-barreled .300 Blackout configurations, featuring a dedicated micro low-profile 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 low-profile design allows unobstructed handguard installation and maintains a clean sight picture when using backup irons or optics.

Quad-Rail Modularity and Brace Stability

The 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 SBA3 adjustable brace complements the quad-rail's versatility by providing a stable, customizable shooting platform that enhances 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.