Maxim Sps Pdx Upper 300blk 5.5"

The Maxim Defense Industries PDX Upper in 300 Blackout with a 5.5" barrel is purpose-built for operators who demand suppressed rifle capability in a compact, modular platform. Designed for law enforcement tactical teams, military special operations, and civilian shooters prioritizing stealth and maneuverability, this upper receiver assembly integrates Maxim Defense's proven SPS (Stateless Piston System) technology to deliver reliable, quiet operation with subsonic ammunition.

The 5.5" barrel length positions this upper as an ideal choice for close-quarters engagement, building breaches, and vehicle operations where ergonomic length and sight radius balance is critical. The SPS piston-driven system eliminates direct impingement, channeling expanding gases away from the receiver to reduce heat signature, fouling, and shooter fatigue during sustained fire—essential advantages in suppressed configurations where subsonic rounds produce minimal audible signature.

Built to mil-spec standards, the upper features a cold-hammer-forged barrel chambered in 300 Blackout, a cartridge renowned for subsonic ballistic performance and use in suppressed rifle systems across military and law enforcement platforms. The modular design allows users to swap bolts, carriers, and components without tools, streamlining maintenance and field adjustments, making it a versatile choice for tactical applications.