The Diamondback DB15 Combo is a semi-automatic rifle chambered in .300 AAC Blackout with a 16-inch barrel, black nitride finish, and a 7075-T6 aluminum receiver. At 6.65 lbs it's light enough for extended handling, and the .300 Blackout chambering works with both supersonic and subsonic loads — the latter being useful if you run a suppressor. 
 

Key Specifications 

• UPC: 810035755079 
• Action: Semi-Automatic 
• Barrel Length: 16 inches 
• Caliber: .300 AAC Blackout 
• Capacity: 30 Rounds 
• Finish: Black Nitride 
• Weight: 6.65 lbs 
   

Features 

 
The adjustable Magpul MOE carbine stock lets you dial in length of pull, which is useful across different shooting positions or when layering gear. The A2 flash hider reduces muzzle flash in low-light situations. The 7075-T6 aluminum receiver is strong for its weight. No sights are included — the design assumes you're mounting an optic, which is the right call for a .300 Blackout setup. 
 
The black nitride finish is harder and more corrosion-resistant than standard phosphate, and holds up to regular field use. Standard AR-pattern magazine compatibility means 30-round PMAG and similar magazines drop right in.

Diamondback DB15 owners in .300 Blackout generally rate it positively, with a few themes that come up consistently.

Reliability gets good marks. Users report smooth cycling with both supersonic and subsonic ammunition, which is relevant for a .300 Blackout rifle that might see suppressed use. The nitride finish draws specific praise for its wear and corrosion resistance compared to standard finishes.

Build quality is generally seen as solid for the price. The 7075-T6 receiver and nitride barrel finish give it a feel that competes well with rifles at higher price points.

Value is a common talking point. The DB15 is frequently described as a good entry point into the .300 Blackout market without overcommitting on price.

Customization options are appreciated. Full AR-pattern compatibility means standard aftermarket parts and accessories fit without issue, which matters to users who want to add optics or modify the platform over time.

Customer service experiences with Diamondback are mixed in online discussions. Most interactions are reported as positive, but some users mention slower response times on warranty or support questions. Worth noting if post-purchase support is a deciding factor.