The Retro MK18 MOD 0 10.5-inch pistol upper from Davidson Defense is a gas-operated assembly chambered in .300 Blackout, built for compact tactical versatility. It features a durable 4150 CrMoV government-profile barrel with a 1:8 twist rate and a nitride finish for enhanced longevity. The system runs on a pistol-length gas system for smooth, reliable operation, but wears a carbine-length quad-rail handguard to provide extended mounting real-estate and the classic MK18 silhouette — the low-profile micro gas block (0.750") is installed beneath that handguard (the A2 F-marked front sight base is not used as a gas block), and the pistol-length gas tube manages pressure accordingly.
The upper uses a 7075-T6 anodized AR-15 receiver and ships with a complete 9310 alloy steel bolt carrier group and a GI birdcage flash hider with 5/8x24 TPI threading. Crisp, compact, and purpose-built, it’s a solid choice for gunsmiths seeking a reliable, high-performance pistol upper.
Caliber: .300 Blackout
Barrel Material: 4150 CrMoV
Barrel Length: 10.5-inch
Barrel Twist Rate: 1:8
Barrel Profile: Government
Barrel Thread Pitch: 5/8x24
Barrel Finish: Nitride
Barrel Gas System Length: Pistol Length
Upper Receiver Name: AR-15 Upper Receiver, M4 Feed ramps
Upper Receiver Material: 7075 T6 Aluminum
Upper Receiver Finish: Anodized
Gas Block Name: Micro Low-Profile Gas Block
Gas Block Size: 0.750
Charging Handle: AR-15 M4 Charging Handle Mil-Spec Quality
Bolt Carrier Name: AR-15 5.56/.223/.300/.350 Complete Bolt Carrier Group
Bolt Carrier Material: 9310 Alloy Steel
Bolt Carrier Finish: Nitride
Muzzle Device: AR-15 5/8x24 TPI GI Birdcage Flash Hider for .308 7.62x39 .300 Blackout
Handguard Style: Carbine-Length Quad-Rail Handguard
Front Sight Base: A2 F-Marked Base
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