The Ruger AR-556 in .300 AAC Blackout (7.62x35mm) is a semi-automatic rifle with a 16.1-inch barrel, 30+1 capacity, and adjustable stock. The .300 Blackout caliber is designed to run effectively in both supersonic and subsonic configurations, making it useful for suppressed setups. 
 

Key Specifications 

• Caliber: .300 AAC Blackout (7.62x35mm) 
• Barrel Length: 16.1 inches 
• Overall Length: 36.25 inches (33 inches with stock collapsed) 
• Capacity: 30+1 rounds 
• Weight: 6.40 lbs 
• Action Type: Semi-Automatic 
• Finish: Black Hardcoat Anodized 
   

Features 

The free-float handguard reduces weight and removes contact between the barrel and handguard, which helps maintain consistent accuracy. M-Lok attachment slots on the handguard accept grips, lights, and other accessories. The single-stage trigger allows for quick follow-up shots without a heavy take-up stage. The six-position adjustable stock fits different shooter sizes and collapses for compact storage. The 1:7-inch barrel twist stabilizes heavier .300 Blackout bullets, covering both subsonic and supersonic loads. 
 

Usage 

The .300 Blackout is a practical caliber in a 16-inch barrel for home defense, hunting small game and predators, and sport shooting. Its main advantage over 5.56 is the ability to run subsonic loads effectively when suppressed, which requires no gas system changes to the rifle. Hunters appreciate the cartridge's terminal performance on medium-sized game at close to moderate ranges.

Owners of the Ruger AR-556 in .300 Blackout tend to focus on the caliber's versatility as the central selling point.

The ability to run both subsonic and supersonic loads effectively in the same rifle comes up consistently. Shooters who run suppressors specifically cite the .300 Blackout's effectiveness with subsonic ammunition as a practical advantage over 5.56 in a suppressed setup. Build quality is described as solid and the semi-auto action as reliable across different ammunition types.

Customization options are appreciated — the standard AR platform means a wide aftermarket is available for handguards, stocks, and triggers.

Common criticisms: weight runs slightly heavier than some competing rifles in class, which a few owners mention as a handling consideration. Factory sights work but several owners upgrade to optics early on for better performance. Overall the AR-556 .300 Blackout is seen as a well-built entry into the caliber without paying a premium over comparable ARs in 5.56.