The SIG SAUER MCX-SPEAR LT 9″ .300 BLK Upper Assembly brings Special Forces–driven innovation to the modern AR platform, delivering a next-generation, piston-driven upper designed for unmatched reliability, modularity, and suppressor optimization. Developed for the SF community, this advanced upper allows you to convert virtually any MIL-SPEC AR-15/M4 lower into a folding, buffer-less firearm with superior durability and performance.

At the heart of the system is SIG’s dual-rod recoil assembly, which eliminates the traditional buffer system and enables the use of folding stocks or braces via a 1913 Picatinny rear interface. The adjustable gas system is tuned for suppressor use, while the short-stroke gas piston design reduces carbon fouling and heat transfer into the receiver for cleaner, longer-lasting operation.

This complete upper features a 9″ nitride-coated, cold hammer forged .300 BLK barrel, a quick-change barrel system, and a removable 3-prong flash hider that is SLH / SLX suppressor-ready with Clutch-LOK compatibility. Built to exceed 20,000 rounds before maintenance part replacement, the MCX-SPEAR LT is engineered for professionals and serious shooters who demand modularity, suppressor readiness, and battlefield-proven reliability.