Maxim Defense PDX 505-SPS 5.56 NATO 5.50-inch Pistol

About this product

What is the Maxim Defense PDX 505-SPS 5.56 NATO 5.50-inch Pistol? It is a legally-defined firearm pistol built around Maxim Defense's Shortened Collapsible Weapon (SCW) system, replacing a traditional buffer tube and stock with an integrated, streamlined rear assembly. This configuration keeps the overall length to just 18.75 inches with a 5.50-inch barrel, creating a highly compact platform. In a market where length-of-pull rules and brace regulations shift, this design sidesteps the ATF Form 1/4 debate by being configured from the factory as a pistol with no stock or brace attached.

What is the Maxim Defense PDX used for?

The PDX 505-SPS is primarily for the shooter who requires an ultra-compact, semi-automatic 5.56 platform for controlled, close-quarters application. Its 5.10-pound weight and 18.75-inch collapsed length make it viable as a vehicle or home defense tool where space is at a premium. The SCW system's single-point QD socket allows for a sling to manage the weapon, as this platform is designed to be fired from a two-handed, unsupported pistol stance not from the shoulder, which is a critical legal and functional distinction.

How does the Maxim Defense PDX compare to a CMMG Dissent piston pistol?

The PDX excels in ultimate compactness, being roughly 6 inches shorter overall than a CMMG Dissent in its most collapsed configuration. The CMMG Dissent operates as a short-stroke piston system offering cooler, cleaner gas management, which is superior for high-volume fire and suppression, while the PDX uses a direct-impingement system shortened via Maxim's proprietary bolt carrier and buffer assembly. For pure minimum package size in 5.56, the PDX is better; for sustained fire characteristics, the Dissent has the edge.

What does it weigh and what are the dimensions?

Unloaded, the pistol weighs 5.10 pounds (81.6 ounces) with an overall length of 18.75 inches. The key dimension is the 5.50-inch barrel, which dictates both velocity and fireball characteristics. The SCW module at the rear adds only 4.25 inches to the receiver extension length when collapsed. For context, this package is approximately 3 inches shorter in overall length than a standard AR-15 pistol with a fully collapsed brace and a 7.5-inch barrel.

Who is this NOT for?

This is not for the first-time rifle shooter or someone looking for a low-recoil, high-velocity plinker. The 5.50-inch barrel will produce significant muzzle flash, substantial blast, and reduced velocity (estimated 2,200-2,300 fps with M193 ball). It's also not for someone who wants to easily shoulder a platform without navigating NFA regulations; attaching a stock requires a Form 1 SBR tax stamp. If your primary use is 100-yard target accuracy, a rifle like the Stevens 334 .308 is a far more suitable choice.

What's in the box?

You receive the complete PDX pistol, one 20-round Magpul PMAG, the QD sling attachment point, and all factory documentation including compliance information. Maxim Defense does not include an optic, sights, or a sling, reflecting its role as a builder-grade platform for experienced shooters. The rifle ships in a foam-padded hard case that is exactly 26.5 inches long, designed to protect the compact investment during transport.

Is the Maxim Defense PDX worth it at $2,245.50?

At this price, it's worth it only for those who specifically need the SCW system's dimensional benefits and are willing to pay for a proprietary, integrally-designed solution. You are paying a premium for engineering that overcomes the physical limitations of a standard AR buffer system in an ultra-short package. If your need for compactness is less extreme, a standard AR pistol build using a quality parts kit and a pistol brace would achieve similar function for several hundred dollars less, though with a longer rear profile. For those wanting a different form of compact utility, consider a Stevens 555 shotgun for a simpler and less expensive close-quarters tool.