The Davidson Defense Marathon 14.5" Carbine-Gas 5.56 NATO AR-15 Pistol Upper Build Kit is built for reliable performance in a compact, compliance-ready platform. It features a 14.5" 4150 CrMoV steel barrel with a phosphate finish, 1:7 twist rate, and a carbine-length gas system paired with a low-profile gas block and stainless steel gas tube for smooth operation.
The included KAK Industry A2 Extended Flash Hider, when installed, brings the overall barrel length to the required length for rifle builds—making this setup pin-and-weld ready, though it has not been permanently affixed. The upper receiver is crafted from 6061-T6 aluminum with an anodized finish, and the 12" aircraft-grade aluminum M-LOK handguard offers lightweight durability and accessory flexibility. This kit is an ideal foundation for builders seeking to create a compact, compliant AR-15 rifle.
Barrel Length: 14.5-inch
Caliber: 5.56x45mm NATO
Barrel Twist Rate: 1:7
Barrel Thread Pitch: 1/2x28
Barrel Finish: Phosphate
Barrel Profile: Government
Barrel Material: 4150 CrMoV
Barrel Gas System: Carbine
Gas Block Size: 0.750
Gas Tube: Carbine Length Stainless Steel Gas Tube AR15
Gas Tube Material: Stainless Steel
Gas Block Profile: Low-Profile
Gas Block Material: Steel
Gas Block Finish: Phosphate
Upper Receiver Material: 6061-T6 Aluminum
Upper Receiver Finish: Anodized
Handguard Length: 12-inch
Handguard Material: Aircraft-Grade Aluminum
Handguard Color: Black
Handguard Style: M-Lok
Muzzle Device: A2 Extended Flash Hider, 1/2x28, Pre drilled hole for pin and weld
Muzzle Device Thread Pitch: 1/2x28
Muzzle Device Finish: Phosphate
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