The Radian Weapons AX556 Builder Kit (Radian part no. R0427) is a matched complete upper and lower receiver set chambered in .223 Remington/5.56 NATO, built around Radian’s Model 1 design philosophy of premium raw materials and precise CNC machining. Every AX556 set is assembled by hand by a trained gunsmith who inspects, test-fires, and cleans the rifle before it ships, and the design carries fully ambidextrous controls so left- and right-handed shooters get equal utility from the same platform. This 10-inch configuration gives builders a compact, pistol-length receiver set ready for the rest of a custom build.

Key Specifications

• Chambered in .223 Remington/5.56 NATO, the standard AR-platform rifle cartridge.
• Sold as a matched lower/upper receiver set, not a bare single component.
• 10-inch configuration suited to a compact, pistol-length build.
• Fully ambidextrous controls give equal utility to left- and right-handed shooters.
• Each set is hand-assembled, test-fired, and cleaned by a trained gunsmith before shipping.
• Semi-automatic fire control group ships installed and ready to complete.
• Finished in black for a clean, tactical appearance.
• Backed by Radian’s lifetime guarantee on every Model 1 receiver set.
• Equipped with Radian’s Raptor-SD charging handle and Talon safety selector.

Frequently Asked Questions

Does this kit include both the upper and lower receiver? Yes, it is a matched receiver set covering both halves of the rifle, not a single component.

What caliber is the AX556 chambered in? .223 Remington/5.56 NATO, the standard AR-platform cartridge.

Are the controls ambidextrous? Yes, Radian builds full ambidextrous controls into every AX556 for equal left- and right-hand use.

Buy the Radian Weapons AX556 Builder Kit Complete Upper/Lower Set 10-inch Black

Order the Radian AX556 Builder Kit from our Radian Weapons lineup of AR15 uppers for fast, insured shipping to your FFL from our Lubbock, Texas gun shop.