The LWRCI ICMKII A5 .300 Blackout 10? SBR Upper in Black is a high-end AR-pattern upper receiver built around LWRC International’s proprietary short-stroke gas piston A5 system, engineered for reliability and ease of maintenance in compact configurations. Designed for the versatile .300 AAC Blackout cartridge, it features a cold-hammer-forged 10? barrel with a 1:7? twist rate and 5/8?-24 TPI threaded muzzle paired with a low-profile, two-position adjustable gas block that allows tuning for suppressed or unsuppressed use. Finished in black Cerakote for corrosion resistance and enduring performance, this upper includes a monoforge one-piece receiver with integrated free-float M-LOK rail, LWRCI Skirmish backup iron sights, and an ambidextrous charging handle. Sold as an upper-only assembly, it’s ideal for building a custom short-barreled rifle (SBR) when paired with a compliant lower and NFA tax-stamp approval. LWRC International LWRCI ICMKII A5 .300 Blackout 10" Bbl Black SBR Upper ICMKIIU3B10S