The Radian Weapons AX556 builder kit (brand part no. R0431) pairs a matched upper and lower receiver set from Radian’s AX556 line, giving builders a coordinated starting chassis engineered by Radian’s in-house design team. Radian Weapons builds the AX556 platform around its own control layout and machining standards, so both halves are designed to work together rather than being sourced separately from mismatched vendors. This builder kit is a fit for shooters who want to start an AX556-based build with a receiver set that’s already proven to fit and function as a matched pair. Among the receiver sets in the AR15 lowers category, the AX556 builder kit is built for shooters standardizing on Radian’s platform.

Key Specifications

• This is a matched upper and lower receiver set from Radian’s AX556 line.
• It is multi-caliber compatible with standard AR-15 upper and bolt combinations.
• The set is built for semi-automatic AR-15 platforms.
• Machined from billet 7075-T6 aluminum for tight, consistent tolerances.
• Finished in Cerakote, available in black, FDE, and Radian Brown.
• Equipped with Radian’s Talon 45/90 ambidextrous safety selector.
• Features Radian’s patented A-DAC ambidextrous bolt-release system, letting right-handed shooters lock the bolt back without leaving the fire control.
• Machined with an integral trigger guard and flared magwell for fast, glove-friendly reloads.
• Uses a SART self-adjusting receiver tensioner to reduce upper-to-lower wobble.

Frequently Asked Questions

Does this kit include both the upper and lower? Yes, it’s a matched receiver set from Radian’s AX556 line.

What platform is this builder kit for? It’s built around Radian Weapons’ AX556 design.

Buy the Radian Weapons AX556 Builder Kit Receiver Set

A matched receiver set engineered as a pair gives an AX556 build a proven starting foundation. Order it from our Lubbock, Texas gun shop for fast, insured shipping to your FFL.