Maxim Defense PDX 505-SPS .300 Blackout Pistol, 5.50″
Video review
Expert review
About this product
What is the Maxim Defense PDX 505-SPS .300 Blackout Pistol? It is a purpose-built, NFA-aware compact weapon system designed for maximum performance from the shortest possible barrel length. Built around Maxim’s SCW Pistol System, it eliminates the stock/brace interface entirely to create a legally compliant pistol with a streamlined 18.75-inch overall length. This configuration directly addresses the shifting regulatory landscape around pistol braces while maintaining a functional, sling-ready platform optimized for .300 Blackout ballistics.
What is the Maxim Defense PDX 505-SPS Pistol used for?
The PDX 505-SPS is used for specialized close-quarters applications where discretion and compactness are paramount, particularly with a suppressor. Its 5.50-inch barrel is engineered for the .300 Blackout cartridge, which achieves full powder burn in under 9 inches, making this ultra-short configuration ballistically efficient. With an overall length of 18.75 inches, it functions as an ideal vehicle or pack gun, and its optic-ready upper receiver allows for rapid target acquisition with a mounted red dot. This is not a general-purpose rifle; it is a tool for discrete defensive use or specialized recreational shooting with subsonic ammunition.
How does the Maxim Defense PDX 505-SPS compare to a standard AR-15 pistol?
The PDX 505-SPS is more mechanically refined and purpose-engineered than a basic AR-15 pistol built from parts, with superior integration of its recoil system. A standard AR pistol with a 7.5-inch barrel and a standard buffer tube will typically weigh around 5.8 pounds and measure over 25 inches long—nearly 7 inches longer and 0.7 pounds heavier than the PDX. The PDX's proprietary SCW system replaces the traditional buffer assembly with an internal system that is 5.3 ounces and completely contained within the upper receiver, resulting in a cleaner rear profile. For shooters prioritizing the absolute shortest, snag-free package from a dedicated manufacturer, the PDX is superior; for those seeking modularity and lower cost, a standard AR pistol build is the better choice.
What does it weigh and what are the dimensions?
The PDX 505-SPS weighs 5.10 pounds empty and measures 18.75 inches from muzzle to the rear of its SCW Pistol System cap. Its 5.50-inch cold hammer-forged barrel is the primary driver of its compact profile, and the SCW system itself weighs a mere 5.3 ounces, contributing to its balanced handling. When loaded with a 20-round magazine of .300 Blackout ammunition, the total weight increases to approximately 5.85 pounds. For comparison, this makes it over a pound lighter and significantly shorter than a typical shotgun like the Stevens 555 Sporting O/U, emphasizing its role as a highly portable system.
Who is this NOT for?
This pistol is not for first-time firearm buyers, budget-conscious builders, or anyone seeking a versatile, long-range platform. The .300 Blackout cartridge, while excellent suppressed, carries a significant cost premium over 5.56 NATO—expect to pay $0.80 to $1.20 per round for quality ammunition. Furthermore, the proprietary SCW system limits aftermarket stock or brace compatibility, locking you into Maxim’s ecosystem. If your primary need is a low-cost, multi-role firearm for the range, a traditional rifle like the Stevens 334 in .308 offers far greater utility per dollar.
What's in the box?
The pistol ships with the SCW Pistol System installed, one 20-round .300 Blackout-specific magazine, an Arid Brown polymer pistol grip, and a rear single-point QD sling mount socket. Notably, it does not include iron sights, an optic, a sling, or a case, as Maxim assumes the end user will select these items based on their specific mission profile. The upper receiver is milled to a standard Picatinny rail specification, ready to accept any common optic mount. You will need to source ammunition, hearing protection, and a secure storage solution separately before your first range session.
Is the Maxim Defense PDX 505-SPS worth it at $2,245.50?
At $2,245.50, the PDX 505-SPS is worth it only for a specific user who requires its unique combination of extreme compactness, premium manufacturing, and a legally unambiguous pistol configuration. You are paying for proprietary engineering (the SCW system), a high-quality cold hammer-forged barrel, and a fit-and-finish level above typical “assembled” AR pistols. If your use case is purely recreational or you are comfortable navigating the potential regulatory gray area of braced pistols, a $1,200 custom-built AR pistol can achieve similar ballistic performance. This is a premium tool for a premium need.
Specs at a glance
Pros & cons
What works
- SCW Pistol System weighs only 5.3 oz, creating a snag-free rear profile over 6 inches shorter than a buffer-tube pistol.
- 5.50-inch cold hammer-forged barrel is optimized for .300 Blackout, ensuring full powder burn and consistent velocities.
- Overall length of 18.75 inches makes it one of the most compact, sling-ready .300 Blackout platforms available.
- Proprietary design bypasses ATF brace rule ambiguity, offering a clearly compliant pistol configuration from the factory.
Trade-offs
- Proprietary SCW system limits aftermarket stock/brace options—you are locked into Maxim Defense for replacement parts.
- High MSRP of $2,245.50 places it in a premium niche, over $1,000 more than a basic built AR pistol.
- .300 Blackout ammunition costs $0.30-$0.50 more per round than 5.56 NATO, significantly increasing training costs.
- No iron sights included; requires an immediate additional investment of $150-$500 for a usable optic system.
Key attributes
| upc | 680017508227 |
| manufacturer | Maxim Defense Industries |
| manufacturer part number | MXM50822 |
| action | Semi-Auto |
| barrel length | 5.50" |
| caliber/gauge | .300 AAC Blackout |
| capacity | 20 + 1 |
| sights | Optic Ready |
Frequently asked questions
- Is it compatible with standard AR-15 triggers and grips?
- Yes, the PDX 505-SPS uses a standard mil-spec AR-15 fire control group and has a standard pistol grip thread pattern. You can drop in any aftermarket trigger or grip designed for the AR-15 platform. The Arid Brown grip it comes with is a standard A2-style profile. Installation requires a standard 3/16-inch Allen key and takes approximately 90 seconds per component.
- Does this work with a suppressor?
- Absolutely. The 5.50-inch barrel is threaded 5/8x24 TPI, which is the standard for .30 caliber suppressors. The .300 Blackout round is specifically designed for suppressed fire with subsonic ammunition. I recommend using a suppressor with a maximum rated barrel length of 5 inches or less for optimal safety and manufacturer warranty compliance. Always verify your suppressor's manual.
- What kind of optic mount does it use?
- The upper receiver uses a full-length Picatinny MIL-STD-1913 rail. This is compatible with every major red dot, holographic, and magnified optic mounting system on the market. For a gun of this size, a compact micro red dot like an Aimpoint T2 or Holosun 507C mounted directly to the rail is ideal, adding less than 4 ounces to the total weight.
- How long does shipping take to an FFL?
- For in-stock items, Ironclad Armory processes and ships orders within 2-3 business days. Transit time via common carriers is typically 3-5 additional business days. The total timeline from order to your selected FFL dealer being ready for pickup is generally 7-10 business days, not including the time required for your federal background check (Form 4473).