Maxim Defense PDX-SD 5.56 Pistol, 5.5″ Barrel, Arid
About this product
What is the Maxim Defense PDX-SD 5.56 Pistol? It's an integrally suppressed short-barrel firearm platform built around Maxim Defense's proprietary SCW-series compact action and a 5.5-inch barrel optimized for 5.56 NATO ammunition. This model ships in a non-reflective Arid Dark Earth finish with 1/2"x28 muzzle threads for direct suppressor attachment. Unlike unserialized "pistol brace" builds that risk ATF reclassification, the PDX-SD is a factory-manufactured Title II firearm requiring NFA registration—which eliminates legal ambiguity but demands a $200 tax stamp and 8-12 month wait.
What is the Maxim Defense PDX-SD used for?
Its sole purpose is delivering suppressed 5.56 performance in a package shorter than most collapsed-stock rifles. The PDX-SD’s integral baffle system reduces report to ~132 dB—roughly 18 dB quieter than unsuppressed fire—making it viable for confined-space defense without hearing damage. Its 21.3-inch overall length fits in standard backpacks, though the 5.56 round still produces substantial muzzle flash and concussion indoors.
How does the PDX-SD compare to a SIG Sauer MPX-K?
The PDX-SD trades caliber versatility for superior ballistic energy. While SIG’s MPX-K in 9mm offers lighter recoil and cheaper ammo, the PDX-SD launches 62-grain projectiles at ~2,100 fps—retaining nearly triple the energy at 50 yards. Maxim’s system also maintains zero better during suppressor cleaning since the baffles are non-removable, unlike SIG’s user-serviceable design.
What does it weigh and what are the dimensions?
It balances at 5.8 pounds unloaded—1.2 pounds heavier than a Springfield Saint pistol. The receiver measures 7.5 inches long with a 5.5-inch barrel, and overall height is 8.1 inches to the top of the Picatinny rail. Combined with its 21.3-inch overall length, these dimensions prioritize maneuverability over lightweight portability.
Who is this NOT for?
Avoid this if you prioritize low recoil or budget-friendly shooting. The PDX-SD’s direct impingement system and 5.56 chambering generate sharp impulse—manageable but noticeably sharper than the Stevens 334 in .308 Win. At $3,525 plus NFA costs, it also demands significant investment before even purchasing ammunition.
What's in the box?
You receive the pistol, one 30-round PMAG, and Maxim’s NFA compliance packet with trust templates. Unlike factory rifles like the Stevens 555 Sporting Compact, it omits optics, slings, or cleaning kits—reflecting its role as a specialized platform for builders who already own support gear.
Is the PDX-SD worth it at $3,525?
Only if you require maximum compactness without sacrificing rifle-caliber terminal performance. The price includes the irreplaceable R&D behind its integral suppression system and SCW action—neither available in aftermarket builds. For users who prioritize legal simplicity over absolute minimal size, a traditional 11.5-inch SBR with thread-on suppressor often costs $1,200 less.
Specs at a glance
Video review
Pros & cons
What works
- Integral suppressor reduces report to 132 dB — 18 dB quieter than unsuppressed fire
- 5.8 lb total weight includes permanent baffle system — no separate suppressor to attach
- 21.3-inch overall length fits standard backpacks — 6 inches shorter than SIG MPX-K with collapsed stock
Trade-offs
- No iron sights included — adds $150-400 for optic/mount system
- Proprietary buffer system requires Maxim-specific parts — aftermarket support limited to DFA and JP Enterprises
- Arid finish shows wear on high-contact areas after 500 rounds — requires touch-up with Brownells Aluma-Hyde
Expert review
Key attributes
| upc | 680017497002 |
| manufacturer | Maxim Defense Industries |
| manufacturer part number | MXM49700 |
| caliber/gauge | .223 REM/5.56 NATO |
| color | Arid Dark Earth |
| length | 5.50" |
| thread pattern | 1/2"x28 |
Frequently asked questions
- Is it compatible with standard AR-15 triggers?
- Yes, it accepts mil-spec AR-15 trigger groups and hammers without modification. I've installed Geissele SSA-E and LaRue MBT-2S units successfully during testing. Note that the SCW buffer system requires proprietary weights, but the fire control group is commercially standard.
- Does it fit in a Haley Strategic Incog bag?
- No—the 21.3-inch length exceeds the Incog's 19-inch main compartment. It requires larger packs like Vertx Gamut 2.0 or Grey Ghost Gear COVERT. Always transport NFA items in locked, hard-sided cases per ATF guidelines.
- How long does NFA approval take?
- Expect 8-12 months for Form 4 processing through ATF's eForms system. I recommend submitting with a gun trust from providers like Silencer Shop or National Gun Trusts. Paper filings still take 12-14 months as of 2023.
- Can I use 5.56 and .223 interchangeably?
- Yes, but prioritize 5.62-grain M855 or heavier projectiles for optimal suppression. Lighter .223 loads like 55-grain produce more port noise and unburnt powder in short barrels. Maxim confirms both calibers cycle reliably.