The Diamondback Carbon DB15 Pistol is a semi-automatic AR-pistol chambered in .300 AAC Blackout with a 10" barrel and Diamondback Black finish. The .300 BLK chambering distinguishes this variant from the 5.56 siblings. It handles both supersonic and subsonic loads, and the 5/8x24 threaded muzzle is sized for standard .30-cal suppressors. 
 

Key Specifications 

• Manufacturer: Diamondback Firearms 
• Family: Carbon Series 
• Model: Carbon DB15 Pistol 
• Type: Semi-Auto Pistol 
• Action: Semi-Auto 
• Caliber/Gauge: 300 AAC Blackout 
• Finish: Diamondback Black 
• Barrel Length: 10" 
• Rate of Twist: 1-in-8 
• Capacity: 30 + 1 rounds (includes one 30rd. PMAG) 
• Weight: 5.7 lbs. 
• Receiver Material: Forged 7075 T6 Aluminum  
• Stock/Grips: Magpul Pistol Grip  
• Sight Type: None (no sights included) 
• Thread Pattern: 5/8x24  
• Safety Features: 2-position thumb safety  
   

Detailed Features 

At 5.7 lbs., this is slightly heavier than the 5.56 variants. .300 BLK components add a small amount of mass. The forged 7075 T6 aluminum receiver is the same across the Carbon Series line, providing a consistent structural baseline. 
 
Magpul MOE Grip and SBA3 Brace are included. The SBA3 adjusts for arm length and folds. One 30-round PMAG ships with the gun. 
 
The 5/8x24 thread pattern is correct for .30-caliber suppressors, which is the primary advantage of this configuration over the 5.56 variants for suppressed shooting. Subsonic .300 BLK runs quietly suppressed; supersonic loads work for standard range use. 
 

Usage Scenarios 

• Home Defense: High-capacity magazine and compact form factor; .300 BLK subsonic loads reduce over-penetration compared to 5.56 
• Sport Shooting: The lightweight build and semi-auto action work well for dynamic stages 
• Suppressed Use: The 5/8x24 threaded barrel is optimized for .30-cal suppressors, and .300 BLK subsonic is one of the quieter suppressed rifle calibers

The Diamondback Carbon DB15 in .300 AAC Blackout gets generally positive feedback from owners who value its light weight and compact size. At 5.7 lbs. with a 10" barrel, it handles easily and the .300 BLK chambering is versatile: supersonic loads for range use, subsonic for suppressed applications.

Range performance with common ammunition is usually acceptable, and recoil is manageable. That said, a number of users have reported feeding or cycling issues with specific ammunition brands or bullet profiles. .300 BLK can be sensitive to ammo selection in some AR-platform pistols, and this gun appears to share that characteristic.

Build quality draws the same comparison to established brands that comes up across the DB15 line. Some owners feel it's a solid value; others think the components don't quite match what higher-priced options offer. Overall sentiment is cautiously positive. People who get a well-functioning example tend to be happy with it, but the reports of reliability issues are frequent enough to suggest testing thoroughly with your intended ammunition before relying on it.