Maxim Defense PDX Upper .300 AAC Blackout 5.5in Matte Black

The Maxim Defense PDX complete upper is a compact, ready-to-install upper receiver chambered in .300 AAC Blackout with a 5.5 inch barrel. Finished in matte black and built to install on Mil‑Spec lower receivers, the PDX balances short overall length with controllability. It incorporates Maxim's HATEBRAKE muzzle booster and uses a direct impingement operating system to suit short-barrel pistol and rifle platforms.

Key Specifications

• The barrel measures 5.5 inches for compact handling.
• The caliber is .300 AAC Blackout.
• The model is designated PDX.
• The finish is Matte with a Black color.
• This item is a Complete Upper Receiver.
• The overall length is listed as 14 inches.
• It uses a Direct Impingement operating system.
• Includes the Maxim HATEBRAKE muzzle booster (patent-pending) to reduce perceived recoil and manage flash and gas direction.
• Compatible with Mil‑Spec lowers for direct installation.

Compact and purpose-built, the PDX upper suits short-barrel pistol and rifle builds where a reduced overall length and controllable .300 AAC Blackout performance are priorities. Its integrated muzzle booster and proven direct impingement design make it a practical choice for operators seeking a concise, serviceable upper for close-quarters and suppressed-capable setups.