Sharps Bros Ambi AR-15 Pistol Lower Build Kit with SBA4 Adjustable Brace

Sharps Bros Ambidextrous Bolt Release AR-15 Pistol Lower Build Kit, SBA4 Adjustable Stabilizing Brace

This is a complete lower build kit designed for AR-15 pistol platforms. It includes everything you need to assemble a functional lower receiver except the serialized lower itself. The kit features a Sharps Bros Gen 2 Livewire receiver in 7075-T6 forged aluminum with an ambidextrous bolt release, paired with an SB Tactical SBA4 adjustable stabilizing brace and a full mil-spec carbine buffer system.

Key Features

• Sharps Bros Gen 2 Livewire lower receiver in 7075-T6 forged aluminum, CNC machined and black anodized
• Ambidextrous bolt release for left and right-handed operation
• Complete mil-spec AR-15 lower parts kit with fire control group and pistol grip included
• SB Tactical SBA4 adjustable stabilizing brace with multi-position adjustment and integrated QD sling socket
• Mil-spec carbine buffer tube, standard carbine buffer, and USA-made carbine recoil spring
• US Tactical mil-spec receiver end plate and AR-15 carbine castle nut
• Threaded bolt catch pin included

Perfect For

• Builders creating AR-15 pistol platforms with ambidextrous controls
• Shooters who prefer adjustable brace systems for comfort and control
• Left-handed or ambidextrous shooters needing dual-sided bolt manipulation
• Pistol builds prioritizing lightweight, forged aluminum construction
• Builders seeking a complete lower kit without sourcing individual components

Design Intent

The Sharps Bros Gen 2 Livewire receiver combines lightweight forged 7075-T6 aluminum construction with precision CNC machining. The ambidextrous bolt release eliminates the need to switch hand positions when manipulating the bolt, a significant advantage for shooters who transition between shoulders or operate with either hand. The receiver is multi-caliber compatible, meaning it functions with any standard AR-15 upper assembly regardless of caliber or configuration.

SBA4 Adjustable Stabilizing Brace System

The SB Tactical SBA4 brace included in this kit offers multi-position adjustment to accommodate different shooting styles and operator preferences. The brace features a reinforced polymer construction with an integrated stabilizing strap and QD sling socket for accessory mounting. The brace mounts to the mil-spec carbine buffer tube via the included castle nut and end plate, providing a secure connection. The adjustable design allows you to customize fit and control for your specific build.

Complete Buffer System

This kit includes all carbine buffer system components: a mil-spec heavy-duty 6-position carbine buffer tube, a standard 3-ounce carbine buffer, and a USA-made carbine recoil spring. The buffer tube accepts the SBA4 brace and is compatible with standard AR-15 carbine buffer systems. The castle nut and end plate secure the buffer tube assembly to the lower receiver.

Lower Parts Kit Details

The included complete mil-spec lower parts kit contains all internal components required to complete the lower receiver: trigger group, hammer, disconnector, selector, magazine catch, bolt catch, and all required pins and springs. These components are assembled into the receiver during the build process and enable semi-automatic operation.

Lower receiver not included. This kit does not include an upper assembly, BCG, or charging handle. Verify all components are compatible with your intended upper assembly before assembly. Follow all manufacturer instructions and ensure compliance with all applicable federal, state, and local laws.