The Maxim Defense PDX SPS is a semi-automatic pistol chambered in 7.62x39mm with a 5.5" barrel and an overall length of 18.75". It holds 20+1 rounds and weighs 5 lbs 9 oz. The receiver is billet aluminum upper and lower, with an Urban Grey polymer grip. 
 

Key Specifications 

• Model: Maxim Defense PDX SPS 
• Caliber: 7.62x39mm 
• Barrel Length: 5.5 inches 
• Capacity: 20+1 rounds 
• Weight: 5 lbs 9 oz 
• Length: 18.75 inches 
• Action Type: Semi-Auto 
• Grip Material: Urban Grey Polymer 
• Stock Material: Synthetic 
• Sights: Optic Ready 
• Special Features: 
  • Direct Gas Impingement System 
  • Billet Aluminum Upper/Lower Receiver 
  • ALG Combat Trigger (ACT) 
  • Dual-Function Safety Selector and Charging Handle 
     

Detailed Features 

The direct gas impingement system keeps the action area cleaner than piston-driven designs, which matters during extended shooting sessions. The billet aluminum upper and lower receivers are machined rather than forged, adding some rigidity and dimensional precision. 
 
The 5.5" barrel keeps the overall package compact. The M4-style flat-top upper is optic-ready so you can mount whatever red dot or magnifier suits the application. The M-LOK free-float forend provides attachment points for lights, lasers, or grips without adding bulk to the barrel. The HATEBRAKE muzzle device is designed to redirect gas and reduce muzzle rise on a short-barreled platform like this one. 
 
The ALG Combat Trigger has a well-documented track record and is a meaningful upgrade over mil-spec triggers. Ambidextrous controls support left- or right-handed operation. 
 

Target Audience 

Compact firearm buyers who want 7.62x39 in a pistol-format AR-style platform. Useful for home defense where maneuverability matters, and for collectors interested in non-standard AR configurations. 
 

Usage Scenarios 

• Home defense where a compact, high-capacity setup in a harder-hitting caliber is preferred. 
• Range use and sport shooting on a compact platform. 
• Tactical training where short overall length is operationally relevant.

The Maxim Defense PDX in 7.62x39mm gets a mixed but generally positive reception, with the price being the most consistent friction point.

The compact dimensions are the main selling point and buyers mention this specifically - at 18.75" overall, it is significantly shorter than a standard AR pistol, and the 5.5" barrel keeps it maneuverable in confined spaces.

Build quality draws consistent praise. The billet aluminum receivers and overall fit and finish are typically cited as above-average for the pistol category. The Urban Gray finish is noted as distinctive compared to standard black.

Performance feedback is generally positive. Owners report reliable cycling across common 7.62x39mm ammunition types and note the HATEBRAKE does reduce muzzle rise noticeably on the short barrel.

Ergonomics get qualified approval. The adjustable brace and ambidextrous controls work well, though some users mention a brief adjustment period for the dual-function charging handle.

Price is the consistent criticism. The PDX sits at a significant premium over comparable short-barrel AR pistols, and buyers debate whether the Maxim-specific features justify the cost difference. Those who have owned it tend to say yes; those evaluating on paper often express skepticism.

Aftermarket support is more limited than AR-15 platforms. The PDX uses some proprietary components, which can complicate certain modifications.