Sig Sauer MPX 9mm 4.5" Bbl Semi-Auto Folding Stock AL MLOK Handguard Black SBR (NFA) w/(1) 35rd Mag RMPX-4B-9-35-SBR

The SIG Sauer MPX 4.5" SBR redefines the standard for modern pistol-caliber carbines by blending submachine gun modularity with duty-grade mechanics. Departing from traditional blowback designs, this premium tactical platform uses a closed-bolt, short-stroke gas piston operating system that dramatically reduces recoil impulse and keeps the receiver free of dirty carbon blowback. The ultra-compact 4.5-inch carbon steel barrel is paired with a free-floating aluminum M-LOK handguard that enables clean placement of weapon lights or switches while providing plenty of ventilation for tucked suppressor configurations. This Gen 3 variant elevates precision via a factory-installed, single-stage flat Timney trigger co-designed to withstand the aggressive cycling speeds of a sub-gun chassis. Complete with an ergonomic polymer grip, an optics-ready top rail, and fully ambidextrous AR-style controls, the platform rounds out its low-profile silhouette with a heavy-duty SIG folding stock that remains fully operational even when collapsed against the receiver flats.