The Radian Weapons AX556 Stripped Billet Lower is a machined AR-15 lower receiver chambered for 5.56 NATO / .223 Remington. It comes finished in brown Cerakote and includes several features that go beyond a standard milspec lower. 
 

Key Specifications 

• Caliber: 5.56 NATO / .223 Remington 
• Condition: New in Box 
• Finish Per Color: Brown Cerakote 
• Manufacturer: Radian Weapons 
• Manufacturer Part Number: R0389 
• Model: AX556 Stripped Billet Lower 
• Type: Lowers (Semi-Automatic) 
• UPC: 817093023737 
   

Detailed Features 

 
The receiver is machined from 7075-T6 aluminum, which is standard in premium AR-15 lowers and provides the strength-to-weight ratio needed for a stripped component that will see long-term use. 
 
The brown Cerakote finish resists corrosion and wear better than anodizing alone. It also produces the brown color that distinguishes this variant from Radian's standard offerings. 
 
An integral trigger guard eliminates the separate pin-in trigger guard that ships with milspec lowers. The flared magazine well speeds up reloads, useful in competition or any scenario where the magazine needs to seat quickly. Radian's Talon 45/90 ambidextrous safety selectors come installed, giving both left- and right-handed shooters the same control placement. 
 
The Self-Adjusting Receiver Tensioner (SART) is a small set screw that takes up play between the upper and lower when they are mated. This reduces the rattle common in milspec-tolerance builds and keeps the fit tight over time. 
 

Target Audience 

 
This lower is for builders who want a billet receiver with Radian's integrated features rather than adding them piecemeal. It fits anyone building a competition, duty, or general-use AR-15 who wants ambidextrous controls and a tight receiver fit from the start. 
 

Usage Scenarios 

 
At the range, the flared mag well and Talon selectors are immediately noticeable during reloads and transitions. For a home defense build, the SART and ambidextrous controls make the finished rifle more usable by any household member regardless of dominant hand.

Owners of the Radian AX556 Billet Lower in Brown Cerakote generally have positive things to say, with a few consistent criticisms.

Build quality is the most praised aspect. The billet construction is noticeably different from a cast or forged lower when you handle it. Surfaces are clean, tolerances are tight, and everything fits without play. People who have built on both milspec and billet lowers notice the difference immediately.

The Brown Cerakote finish gets a lot of attention because it is uncommon. Most AR-15 builders default to black or FDE, so brown Cerakote stands out. Buyers who chose this variant specifically for the color tend to be happy with it; buyers who wanted a different color and settled for brown are less enthusiastic.

The ambidextrous Talon selectors draw consistent praise from left-handed shooters and people who train for both hands. Right-handed-only users sometimes find the left-side selector paddle gets in the way until they get used to it.

Compatibility is broadly good. The AX556 mates with standard AR-15 uppers without fitting issues, and Radian's SART takes up any remaining slop between the upper and lower.

Price is the main sticking point. The AX556 stripped lower costs considerably more than a milspec forged lower, and some buyers question whether the integrated features justify the difference when those same features can be added to a cheaper lower for less. Buyers who do the math on individual Radian components (Talon selectors, separate integral trigger guard options) often conclude the AX556 is fairly priced when bundled. Others feel the billet premium is not worth it for a stripped receiver.

Customer support feedback from Radian is generally positive, though response times vary.