TacFire SS-RK556-LPK AR-15 Lower Parts Kit 5.56 NATO / .223 Rem 16" Barrel Black Nitride

The TacFire SS-RK556-LPK is an unassembled AR-15 rifle build kit chambered in 5.56x45mm NATO / .223 Remington, bundling the major upper and lower components a builder needs to complete a mil-spec semi-automatic carbine from a stripped lower receiver.

At the core of the kit is a 16-inch M4 contour barrel finished in Black Nitride and threaded 1/2"-28 to accept a standard .223/5.56 muzzle device or suppressor mount. A 1:8 twist rate stabilizes the full spread of .223 and 5.56 bullet weights. A birdcage flash hider and crush washer are included for out-of-the-box muzzle readiness.

The barrel is paired with a 15-inch M-LOK free-float handguard for a slim, lightweight profile and modern accessory mounting. Combined with the included upper receiver components and the USA-made lower parts kit, the SS-RK556-LPK delivers the major parts required to assemble a custom AR-platform rifle.

The lower parts kit ships with mil-spec components for the fire control group, magazine catch, bolt catch, safety selector, buffer retainer, and pistol grip, along with the springs, detents, and pins needed for assembly. A mil-spec trigger comes standard. The semi-automatic action is built around the standard AR-15 platform and is compatible with any mil-spec stripped lower receiver.

Constructed from aluminum components with a uniform matte black finish, the SS-RK556-LPK is a turnkey bundle for first-time builders, gunsmiths, or anyone assembling a custom AR-15 rifle. Stripped lower receiver and buttstock assembly are not included.