Update, October 9, 2026: ATF no longer requires a Form 4, tax stamp, fingerprints or registration for suppressors, short-barreled rifles, short-barreled shotguns or AOWs. They now transfer on a standard Form 4473 with a background check. Anything below that mentions a Form 4, a wait or a tax stamp was written before this change. What changed
⚠ SHORT BARREL RIFLE (SBR) — NO FORM 4 REQUIRED Since October 9, 2026, ATF no longer requires a Form 4, tax stamp, fingerprints or registration for short-barreled rifles. It transfers on a standard Form 4473 with a NICS background check. Your state’s law still applies, and taking one across state lines still needs an approved ATF Form 5320.20. Outside Texas, we ship to an SOT dealer in your state. What changed · How buying one works now
The Maxim Defense SDX:508 is an integrally suppressed Short Barrel Rifle built to SOCOM-grade specifications. The SDX platform was developed from the U.S. Special Operations Command PDW solicitation — engineered for Tier 1 operators who demand maximum firepower in minimum length. At its core is the DSX-D suppressor with MonoKore™ Technology, a single-piece monocore baffle stack that Maxim Defense calls the most robust suppressor in its category. SOCOM table-tested across multiple calibers with no damage and no significant change in sound reduction. The SDX:508 runs 5.56 NATO, 7.62×39, and .300 BLK from its 8.5" barrel, with an overall length of 28.125" — hearing-safe, full-powered, and NFA-registered as a single unit.
Construction is military-grade throughout: 6Al-4V titanium and 17-4 stainless steel baffles, 7075-T6 and 6061 aluminum receivers, and a Diamond-Like Coating (DLC) finish with Type III hard coat anodizing. The HK-height rail delivers a more rigid upper receiver for optics. Arid (Flat Dark Earth) Cerakote finish. Manufactured in the USA. ISO 9001:2015 certified.
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.
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This item is out of stock. These are on the shelf today and ship or transfer the same way. Not sure which is the right swap? Call 817-393-4000 and we will tell you straight.
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