Maxim Defense PDX Upper | .300 AAC Blackout | 5.5″

The Maxim Defense PDX Upper is a complete upper receiver configured for .300 AAC Blackout with a 5.5″ barrel and a matte black finish. It is designed for installation on Mil‑Spec lower receivers and uses a direct impingement gas system. The upper includes Maxim’s HATEBRAKE muzzle booster, a device that redirects gas and concussion forward to mitigate rearward blast in short-barrel configurations.

Intended for compact SBR builds and close-quarters or short-range training, this upper provides a compact, controllable platform where overall length and suppressed performance matter.

Product Specifications

• The manufacturer is Maxim Defense Industries.
• The model is listed as PDX.
• The caliber/gauge is .300 AAC Blackout.
• The barrel length is 5.5″.
• The finish is described as Matte.
• The color is Black.
• The product type is a Upper receiver.
• The subcategory is Complete Upper Receivers.
• The system uses a Direct Impingement gas operation.
• The muzzle device is the patent-pending Maxim HATEBRAKE Muzzle Booster.
• The overall length is listed as 14″ in the manufacturer description.
• This upper is designed to install on Mil‑Spec lower receivers.
• The intended applications include compact SBR builds and close-quarters/short-range training.
• The UPC is 680017478278.

For users building compact AR platforms where reduced overall length and controlled blast are priorities, the Maxim Defense PDX Upper presents a purpose-driven component set that retains standard AR ergonomics. Its short barrel and dedicated muzzle booster make it suitable for suppressed short-range work and training drills that prioritize maneuverability and signature management.