Sig Sauer MPX 9mm 4.5" 35rd Folding Stock SBR

The MPX runs a closed bolt gas piston system instead of the simple blowback most 9mm carbines use, and that operating system is the core of the platform. This is the short barrel rifle build: a 4.5" barrel on an SBR receiver, which makes the gun compact before you ever fold the stock.

And it does fold. The Sig folding stock swings flat against the side of the gun and the MPX still runs in the folded position. That matters in a vehicle or a pack, not just in a case. The handguard is aluminum with M-LOK slots for lights, hand stops and sling hardware, and Sig offers that handguard in several lengths, including longer tubes cut to cover a suppressor. A 35 round magazine comes with the gun. If you want a modular 9mm subgun with a real stock behind a barrel this short, the SBR is the configuration Sig builds it in, and the folding stock is what separates the current gun from the MPX generations that came before it.