Rock River Arms' new PDS (Piston Driven System) Carbine utilizes the company's new PDS system with a purpose-designed bolt carrier, adjustable gas piston, and over-the-barrel spring and guide rod arrangement. The PDS Carbine has a full-length top mounting rail for flexible placement of numerous accessories. Its RRA side-folding six-position Tactical CAR stock features a receiver extension storage compartment, and folding ambidextrous, non-reciprocating charging handles may be used independently or in unison. The PDS Carbine also features the RRA two-stage trigger and a two-position adjustable regulator.