Maxim Defense Industries SDX-508, Short Barreled Rifle, 300 Blackout, 8.5″ Threaded Barrel, Cerakote Finish, 300BLK SBR Black

Product Description

Maxim Defense SDX:508 Integrally Suppressed SBR — .300 BLK / 5.56 / 7.62×39 — Black

The Maxim Defense SDX:508 Black is the standard black finish variant of Maxim’s SOCOM-lineage integrally suppressed Short Barrel Rifle. The DSX-D suppressor with MonoKore™ Technology — a single-piece monocore baffle system — is SOCOM table-tested and rated as the most robust suppressor in its category. Runs 5.56 NATO, 7.62×39, and .300 BLK from an 8.5" barrel. 28.125" overall. Black Type III hard coat anodized finish over 6Al-4V titanium and 17-4 stainless steel construction. Gen. 7 CQB Stock. HK-height rail. Made in USA. ISO 9001:2015 certified.

Maxim Defense Industries: Purpose-Designed, Duty-Built

Maxim Defense Industries is a Minnesota-based American firearm manufacturer and ISO 9001:2015 certified company. The PDX and SDX platforms were developed directly from the SOCOM PDW solicitation — designed to meet the demands of Tier 1 operators who need maximum lethality in a minimum package. Maxim Defense builds its firearms from military-grade materials: 6Al-4V titanium, 17-4 stainless steel, 7075-T6 and 6061 aluminum. Every firearm is built to order in the USA.

Frequently Asked Questions

What is an SBR? A Short Barrel Rifle has a rifle barrel under 16″ and is federally regulated as an NFA item. Since October 9, 2026 it needs no Form 4 or tax stamp: it transfers on a standard Form 4473 with a background check.

What calibers does the Maxim Defense PDX/SDX fire? All PDX and SDX models are offered in 5.56 NATO, 7.62×39, and .300 BLK. .300 BLK pairs best with an integral suppressor for hearing-safe suppressed fire.

Does the SDX/PDX-SD come with the suppressor? Yes — the integrated DSX-D (SDX) or PDX-specific suppressor is included. The suppressor is part of the registered SBR and is not sold separately.

How long does NFA approval take? Typically 30–90 days. Western Sport holds the SOT, and since October 9, 2026 there is no Form 4 to file.

Is the $0 NFA tax stamp permanent? The OBBBA eliminated the $200 NFA tax. Western Sport recommends calling to confirm current status.

Ordering from Western Sport

Order online and we ship it to the licensed FFL dealer you choose near you — see how buying a gun online works. Western Sport has been a licensed FFL/SOT dealer since 2007, and everything we sell carries the full manufacturer warranty. Questions before you order? Send us a message.

Additional information