The Davidson Defense Marathon 14.5" Carbine-Gas 5.56 NATO AR-15 Pistol Full Build Kit is designed for builders seeking precision, reliability, and compliance-ready performance. It features a 14.5" government profile barrel made from 4150 CrMoV steel with a phosphate finish, 1:7 twist rate, and a carbine-length gas system paired with a 0.750 gas block for smooth, consistent cycling.
The included KAK Industry A2 Extended Flash Hider, when installed, brings the barrel length to meet rifle standards, making the kit pin-and-weld ready—though not yet permanently attached. The Black Diamond Series billet upper and 12" ultra-lightweight M-LOK handguard strike a balance between strength and weight. The kit also includes a Gauntlet Arms stabilizing brace, complete bolt carrier group, mil-spec charging handle, and heavy-duty pistol buffer tube—providing everything needed for a dependable and regulation-ready AR-15 build.
Caliber: 5.56x45mm NATO
Barrel Length: 14.5-inch
Material: 4150 CrMoV
Thread Pitch: 1/2x28
Finish: Phosphate
Profile: Government
Twist Rate: 1:7
Gas System: Carbine
Gas Block Size: 0.750
Name: A2 Extended Flash Hider
Upper Receiver: Black Diamond Series AR-15 Billet Upper Receiver
Handguard: AR-15 Ultra-Lightweight Minimalist Handguard 12" M-LOK
Bolt Carrier Group: AR-15 5.56/.223/.300/.350 Complete Bolt Carrier Group
Charging Handle: AR-15 M4 Charging Handle Mil-Spec Quality
Pistol Brace: Polymer Stabilizing Brace - Black
Buffer Tube: Heavy Duty Pistol Buffer Tube for AR-15
Recoil Buffer: AR-15 Standard Carbine Recoil Buffer - 3 oz.
Recoil Spring: Standard AR-15 Carbine Recoil Spring
End Plate: AR-15 M16 Mil-Spec Receiver End Plate - Black
Castle Nut: AR-15 Carbine Castle Nut - Black
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