Davidson Defense Marathon 14.5" 5.56 AR-15 Pistol Build Kit, KAK A2 Flash Hider, w/ Gauntlet Arms Brace

Marathon 14.5" 5.56 AR-15 Pistol Build Kit, KAK A2 Flash Hider, w/ Gauntlet Arms Brace

This is a complete pistol build kit designed for shooters who want a compact 5.56 platform with the option to pin and weld the muzzle device for legal compliance. The kit includes everything except the lower receiver, with a carbine-length gas system, 12-inch M-Lok handguard, and a stabilizing brace for pistol configuration. The 14.5-inch barrel comes paired with a KAK Industry A2 Extended Flash Hider that's pre-drilled for pin and weld, bringing total length just over 16 inches when permanently attached.

Key Features

• 14.5-inch 4150 CrMoV barrel, 1:7 twist, phosphate finish for 5.56 NATO
• Carbine-length gas system with low-profile gas block
• Black Diamond Series billet upper receiver, USA made, Type III hard coat anodized
• 12-inch M-Lok aluminum handguard for accessory mounting
• Complete bolt carrier group in 9310 alloy steel with nitride finish
• KAK Industry A2 Extended Flash Hider, pre-drilled for pin and weld
• Mil-spec lower parts kit, buffer tube, buffer, and recoil spring included
• Polymer stabilizing brace for pistol configuration

Perfect For

• Shooters building a compact 5.56 pistol with legal pin and weld capability
• Builders who want a complete kit minus only the serialized lower receiver
• Those seeking a carbine-length gas system in a shorter platform
• Shooters planning to pin and weld the muzzle device for 16-inch overall length compliance

Pin and Weld Ready Configuration

The A2 Extended Flash Hider arrives pre-drilled for permanent attachment, eliminating the need to source a separate pin and weld hole. Once pinned and welded to the 14.5-inch barrel, the muzzle device brings total rifle length to just over 16 inches, meeting federal length requirements for permanent muzzle device attachment. This setup allows you to maintain the compact pistol configuration while achieving a legal overall length through permanent muzzle device installation. The pin and weld process itself requires no additional gunsmithing tools beyond basic hardware, making this a straightforward path to a compliant rifle configuration.

Carbine-Length Gas System Performance

The carbine-length gas tube paired with the low-profile gas block provides reliable cycling in a compact platform. This gas system length is optimized for 14.5-inch barrels and delivers consistent bolt carrier movement without excessive recoil impulse. The stainless steel gas tube resists corrosion, and the low-profile design maintains a clean sight picture when using iron sights or optics mounted on the upper receiver.

Follow safe handling and manufacturer instructions. Ensure compliance with all applicable federal, state, and local laws. Lower receiver not included. BCG and charging handle are not included in this kit as separate items but are provided as part of the complete build kit.