The Maxim Defense PDX is an AR-pattern semi-automatic rifle chambered in .300 AAC Blackout with a 5.5-inch barrel. It holds 20 rounds and ships in a Flat Dark Earth finish. The 5.5-inch short-barreled configuration requires additional federal paperwork for transfer. 
 

Key Specifications 

• Brand: Maxim Defense 
• Model: PDX 
• Caliber: .300 AAC Blackout 
• Action: Semi Auto 
• Capacity: 20 Rounds 
• Barrel Length: 5.5 in 
• Color/Finish: Flat Dark Earth 
   

Detailed Features 

• 5.5-inch barrel in a short-barreled configuration; transfer requires additional federal paperwork 
• 20-round capacity in .300 AAC Blackout 
• Flat Dark Earth finish throughout 
• AR-pattern platform in a compact PDX layout 
• .300 AAC Blackout chambering suited for both supersonic and subsonic loads

Owners of the Maxim Defense PDX pick it for its compact footprint. The 5.5-inch barrel makes it genuinely short, and most owners run it specifically in situations where overall length matters. The .300 AAC Blackout chambering adds versatility, with owners switching between supersonic and subsonic loads depending on the application.

The Flat Dark Earth finish is consistently noted as well-applied and durable. Build quality on the PDX draws strong reviews overall, with tight tolerances and a fit that matches or exceeds similarly priced AR-platform options. The trigger gets mixed marks: functional out of the box, but a common upgrade target for owners who spend time at the range.

The additional federal paperwork required for the short-barreled configuration is the main barrier for new buyers, and some owners note that the process adds time and cost to acquisition. For those already familiar with that process, the PDX delivers a capable and well-built package. Suppressor compatibility in .300 AAC Blackout is a frequent topic in owner discussions, with most finding the platform well-suited to running a can.