Maxim Defense PDX Upper .300 AAC Blackout 5.5″

The Maxim Defense PDX upper is a compact, complete upper receiver designed for short-barrel AR builds in .300 AAC Blackout. It pairs a 5.5″ barrel with an integrated Maxim HATEBRAKE muzzle booster and is built to mount on Mil‑Spec lower receivers. The assembly uses a direct impingement gas system and a matte black finish intended for low-visibility handling and compact carry configurations.

Key Specifications

• The barrel measures 5.5 inches for a compact profile suitable for short-barrel builds.
• Chambering is .300 AAC Blackout.
• The model designation is PDX.
• This item is a Complete Upper Receiver.
• The finish is Matte Black.
• Designed to install on Mil‑Spec lowers.
• The operating system is Direct Impingement.
• Equipped with the Maxim HATEBRAKE Muzzle Booster (patent-pending).
• The described overall length is 14 inches in the configuration noted by the manufacturer.

Engineered for compact performance, the PDX upper packs modern components into a short-barrel package that suits close-quarters and compact carry configurations. The included HATEBRAKE muzzle device and direct-impingement system make this upper a straightforward option for builders seeking a purpose-built .300 AAC Blackout solution in a matte black finish. Add the PDX upper to a compatible Mil‑Spec lower to complete a compact, reliable AR configuration without unnecessary complexity.