The Diamondback DB15 Combo (Diamondback part no. DB1721K061) is a two-caliber AR-15 package that ships with a complete 5.56 NATO upper and a second complete .300 AAC Blackout upper, letting one lower receiver serve two distinct roles. Diamondback Firearms builds both uppers around a gas-impingement system with CNC-machined components and 4140 chrome moly barrels, and finishes the carbon-fiber-reinforced lower in Flat Dark Earth. A 12-inch M-Lok handguard, Magpul MOE grip, and Magpul MOE carbine stock complete a rifle built for shooters who want the flexibility of two calibers without buying two complete guns.

Key Specifications

• Includes complete uppers for both 5.56 NATO and .300 AAC Blackout.
• Barrel length is 16 inches on both uppers.
• Rate of twist is 1:8 inches.
• Both uppers use an A3 flattop receiver for direct optic mounting.
• The gas system is carbine-length direct impingement.
• The handguard is a 12-inch M-Lok free-float design.
• The grip is a Magpul MOE grip.
• The stock is a Magpul MOE carbine stock.
• The muzzle wears an A2 flash hider.
• The lower receiver is carbon-fiber reinforced, finished in Flat Dark Earth.

Frequently Asked Questions

What does this combo include? A complete 5.56 NATO upper and a complete .300 AAC Blackout upper, both fitting the same lower receiver.

What magazine capacity does it ship with? 30+1 rounds.

What is the lower receiver made from? A carbon-fiber reinforced polymer, finished in Flat Dark Earth.

Buy the Diamondback DB15 Combo Rifle, 5.56 NATO & .300 Blackout, 16-inch, Two Uppers

This two-caliber DB15 combo adds flexibility to our AR rifles lineup. Order it from our Lubbock, Texas gun shop for fast, insured shipping to your FFL.