The suppressor market has exploded over the last few years. New designs, new mounting systems, and new manufacturers seem to appear almost monthly, making it increasingly difficult for companies to introduce something that genuinely stands apart. That's exactly why the Novox Research X-SD caught my attention.
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We first saw the X-SD during SHOT Show when Novox founder Jacob flagged us down at the Vanguard Arms booth to show us a prototype. Since then, we've had the chance to watch the system evolve from an interesting concept into a finished production product. After spending considerable time behind one of the latest versions paired with a Richmond Tactical RT9 PCC, I think Novox has brought something to market that fills a niche very few products currently occupy.
Where a suppressor primarily reduces muzzle blast, the X-SD tackles another major source of noise: the supersonic crack. By bleeding off pressure before the bullet leaves the barrel, the system reduces projectile velocity, allowing many common off the shelf 9mm loads to reach subsonic speeds. The result is a quieter shooting experience while maintaining a compact overall package.
What is the Novox X-SD?
At its core, the XSD is a barrel conversion kit designed to work alongside your existing suppressor.
The system consists of four primary components: a 4.3-inch ported barrel with a 1:10 twist, a taper adapter, the main extension tube, and your choice of suppressor mounting module. The barrel threads into the taper adapter, which uses an internal taper lock rather than O-rings to create a secure seal. From there, the extension tube threads onto the adapter and forms the main body of the system. At the front, the tube accepts either an Alpha or Bravo/HUB mounting module. Both are included with every kit, making the X-SD compatible with the vast majority of suppressors on the market right out of the box.
How Does the X-SD Work?
Unlike a traditional barrel, the XSD's barrel is ported.
As the bullet travels down the bore, a portion of the expanding gases is vented through those ports into the chamber created by the extension tube before the projectile reaches the muzzle. By bleeding off pressure before the bullet exits, the system reduces muzzle velocity enough to bring many standard velocity factory loads into the subsonic range.
At the same time, the reflex style design places additional suppressor volume rearward over the barrel instead of adding all of that length to the front of the firearm. More internal volume generally translates to better sound reduction while keeping the overall package shorter than many conventional suppressor setups.
The practical advantage is simple. Instead of hunting down expensive specialty subsonic ammunition, the X-SD allows shooters to use many commonly available factory loads while still enjoying much of the benefit that subsonic ammunition provides when paired with a suppressor.
Installation Considerations
One aspect I appreciate about the X-SD is that it remains relatively low profile.
Depending on your existing setup, you may be able to retain your current barrel nut and handguard without switching to a larger diameter rail. However, clearance is still something worth paying attention to. The closer your handguard sits to the X-SD and the suppressor, the more heat will be transferred into the rail during extended firing sessions.
Some tighter fitting handguards may also prevent the use of certain MLOK or KeyMod accessories due to clearance limitations. It's something to keep in mind when planning a build.
The Richmond Tactical RT9PCC
For this review, Novox partnered with Richmond Tactical to offer the X-SD as a factory-installed option on their RT9PCC pistol.
The RT9 PCC is a direct-blowback AR-9 featuring a billet receiver set with a slick-side upper and a flared magwell that accepts Colt-pattern magazines. It comes equipped with 45-degree Ambi Enhanced selectors, a Die Free Co. Kung Fu Grip, and an SBA3 brace fitted with a thicker Phase 5 strap. Fire control is handled by a mil-spec trigger that broke between 3 and 5 pounds on our sample.
Originally, Richmond Tactical equipped these rifles with an Armaspec Sound Mitigation Buffer. Since receiving our sample, they've transitioned to a more traditional 10-ounce buffer to improve compatibility with FRT triggers and selectors.
The XS-D equipped RT9 also features a 7.25-inch Midwest Industries suppressor handguard that provides additional clearance around the conversion kit while allowing the suppressor to sit partially recessed beneath the rail. Paired with Richmond Tactical's RT9SG suppressor, it creates a clean, well-balanced package that's as visually appealing as it is functional.
On the Range
Straight-blowback PCCs have developed a reputation for having a surprisingly sharp recoil impulse. Despite firing relatively mild pistol cartridges, the heavy reciprocating bolt often produces a recoil impulse that feels more abrupt than many shooters expect.
That wasn't my experience here.
With the Armaspec Buffer, the RT9PCC proved to be an exceptionally soft shooting PCC. Recoil was smooth, muzzle movement stayed minimal, and the rifle remained easy to control during both rapid strings of fire and controlled pairs.
The combination of the RT9, the XSD, and the suppressor also made for an extremely pleasant shooting experience from an audible standpoint. Indoors, the direct-blowback operating system still produced the gas blowback most shooters would expect from a suppressed PCC, but that's more of a characteristic of the platform than a criticism of the XSD itself.
Velocity Testing
Since reducing velocity is the entire premise behind the XSD, we wanted to put numbers behind the claims.
Using several common factory loads, we recorded the following average velocities:
The results were impressive. Nearly every load we tested landed at or below the speed of sound, producing the kind of subdued report most shooters associate with dedicated subsonic ammunition.
That said, I'd still recommend wearing hearing protection. Bulk factory ammunition can vary slightly from lot to lot, and an occasional hotter round may still break the sound barrier. While we didn't experience that during testing, I'll remind you that hearing loss is permanent. Shooting a magazine or two without ear pro from time to time probably isn't the end of the world, but I certainly wouldn't make a habit of it.
Can You Shoot the XSD Without a Suppressor?
Technically, yes.
Without a suppressor installed, the XSD behaves much like a blast diffuser or linear compensator. It still functions properly, but the difference in sound compared to running a suppressor is substantial.
If you're planning to run the XSD without a suppressor attached, hearing protection should absolutely be considered mandatory.
Reliability and Maintenance
Over the course of testing, we fired somewhere between 800 and 1,000 rounds through the rifle.
Reliability was excellent throughout our evaluation.
The one thing I did notice was how dirty the rifle became during extended shooting sessions. That's hardly surprising considering you're combining a suppressed firearm with a direct-blowback operating system. Carbon accumulation comes with the territory.
As long as you're willing to stay on top of routine cleaning and maintenance, it shouldn't present any issues.
What's Coming Next?
One of the most exciting aspects of the XSD isn't where it is today, it's where Novox plans to take it.
Current support already includes AR-9s and the CZ Scorpion, while upcoming kits are nearing completion for the B&T SPC9 and GHM9, Springfield Armory Kuna, CMMG RDB platform, Stowaway 9, VZ.61, .45 ACP AR platforms, and 300 Blackout.
Further down the road, the company is also exploring support for the HK UMP, Grand Power Stribog, Matador 9, PSA AKV, and additional platforms.
Personally, the Sten Mk II conversion is the one I'm looking forward to the most.
Who Is the XSD For?
If you're someone who enjoys suppressed PCCs or PDWs and wants quieter performance without relying exclusively on expensive specialty ammunition, I think the XSD makes a compelling case.
It's also appealing for shooters who already own an AR-9 or Scorpion and would rather retrofit an existing firearm than purchase an entirely new suppressor ready platform. At roughly $400 for the conversion kit, it's a considerably more approachable investment than buying a new firearm.
On the other hand, if maximizing terminal performance is your primary concern, this probably isn't the system for you. The entire purpose of the X-SD is to reduce velocity. That's exactly what makes it quieter, but it also means you're intentionally giving up some muzzle energy in the process.
Likewise, owners of 16-inch PCCs should keep overall barrel length in mind. Depending on your configuration, installing the XSD may require either converting the firearm into a short-barreled rifle or permanently pinning and welding components to remain compliant.
Final Thoughts
After spending significant time with the Novox XSD and the Richmond Tactical RT9PCC, I came away impressed.
The RT9 proved to be reliable, soft shooting, and enjoyable to run, while the X-SD delivered exactly what it promises: a practical way to achieve quieter performance from common factory ammunition. More importantly, it accomplishes that without asking shooters to abandon suppressors they already own or invest in an entirely new firearm.
Whether the tradeoff between reduced velocity and increased sound suppression is worth it will ultimately depend on your priorities. For shooters chasing maximum terminal performance, it probably isn't. But for suppressor enthusiasts, PCC fans, and anyone looking to stretch the capabilities of common factory ammunition, the XSD offers an innovative solution that currently has very little competition.
