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There are short ARs, and then there is the PDX. Maxim Defense built this thing to answer the SOCOM PDW solicitation, and it shows in every detail. At just 18.75 inches overall with a 5.5 inch barrel, it is one of the most compact .300 Blackout platforms you can put your hands on, and RECOIL Magazine gave it Best of SHOT honors back in 2019 for good reason. This is a purpose-built tool for tight spaces, vehicle work, and home defense setups where every inch matters.
The trick is Maxim's patented SCW system. Instead of a standard buffer tube, the bolt carrier group is integrated into a shortened recoil system with interchangeable buffer weights, which cuts the brace assembly down to just 4 inches. That is how you get a legit AR platform this compact without giving up reliability. Interchangeable weights also let you tune the gun to your ammo, whether you are running supersonics at the range or subsonics through a can.
A 5.5 inch .300 Blackout barrel would normally mean serious blast and flash. Maxim solved that with the HATEBRAKE muzzle booster, tucked under the handguard and installed from the factory. It cuts recoil, knocks down the flash signature, and pushes gas and concussion downrange instead of back into your face. It also adds a bit of tuned backpressure, so the short gas system runs consistently. The .300 Blackout chambering is the natural pick here since the cartridge was designed to burn efficiently in stubby barrels.
Maxim did not cheap out on the small stuff either. You get an ALG Combat Trigger, a Radian Raptor ambidextrous charging handle, ambi controls, and an M-LOK handguard with a full-length top rail ready for your optic and light. Construction leans on 7075 and 6061 aluminum, 17-4 stainless, and titanium components with a hard anodized black finish. Add the 20 round magazine and 5/8×24 threaded muzzle, and this is a complete, suppressor-ready PDW right out of the box.
Yes, the 5.5 inch barrel comes threaded 5/8×24, and the platform was designed with suppressed use in mind. Maxim built the HATEBRAKE to create backpressure similar to their DSX suppressor, so the gun cycles consistently whether you run the brake or swap it for a can. Pair it with subsonic .300 Blackout loads and it makes a very quiet package.
The .300 Blackout cartridge was designed to burn its powder charge in very short barrels, so you lose far less velocity than you would with 5.56 out of the same length. Even from 5.5 inches, the PDX pushes supersonic loads around 1,850 fps on average. That means real terminal performance from a gun under 19 inches long.
Maxim's patented SCW system integrates the bolt carrier group with a shortened recoil assembly and interchangeable buffer weights, eliminating the need for a full-length buffer tube. That cuts the brace section down to just 4 inches, which is how the PDX achieves its 18.75 inch overall length. The swappable weights also let you tune cycling for different loads.
Yes. The PDX in .300 Blackout uses standard AR-15 pattern magazines, and it ships with one 20-round mag. Since .300 Blackout shares case head dimensions with 5.56, your existing AR mags will feed it, though dedicated .300 BLK marked mags are a smart way to avoid mixing up ammo.
| UPC | 680017478230 |
|---|---|
| Manufacturer | |
| Manufacturer Part Number | MXM-47823 |
| Action | |
| Barrel Length | 5.5" |
| Caliber/Gauge | .300 AAC Blackout |
| Capacity | 20 |
| Color | Black |
| Model | |
| Product Type | AR |
| Safety | Manual Safety |
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