Reviews Suppressed Maxim Defense SDX RFLX Rifle: Integrated, Not Intergral [REVIEW] Dave Merrill February 23, 2026 Join the Conversation At RECOIL, we review every product fairly and without bias. Making a purchase through one of our links may earn us a small commission, and helps support independent gun reviews. Read our affiliate policy. Find out more about how we test products. It’s hard to standout at CANCON with a good suppressed rifle — a place where everything is suppressed, and every silencer is better this year than it was the last. But at CANCON Arizona in 2025, Maxim Defense stuck out with their new SDX RFLX, a quiet and smooth-shooting .300BLK rifle. It was 2021 the first time we shot an experimental SDX, then a very different gun, but the roots of the suppressed Maxim Defense RFLX go back much further than that. The seed was first planted way back in 2016, when the U.S. Special Operations Command opened a solicitation for an M4 upper with a built-in silencer, called the Suppressed Upper Receiver Group (SURG). The tale of the SURG is worthy of an article itself, but needless to say, the engineers at Maxim Defense were unimpressed with what they saw produced for the program — and sought to do the concept better. To be clear, the RFLX in this article isn’t a SURG submission, but it’s what got the gears moving. Over the years the main public draws at Maxim Defense have been the shorty PDX PDWs and M240 silencers, but the SDX RFLX was being designed and refined in the background — and now we can give it a closer look. FEATURES & DETAILS Maxim Defense SDX RFLX, SBR Carbine Caliber: .300BLK Barrel Length (sans silencer): 8.5 inches Overall Length: 30.5 inches (stock collapsed), 34.25 inches (stock extended) Capacity: 20, 30 Weight (unloaded): 7 pounds, 14 ounces MSRP: $3,695 URL: maximdefense.com Accessories: EOTech EXPS3-DCR, TAN $819 EOTech OGL, Commercial $2,999 The core of the SDX RFLX is an 8.5-inch .300BLK barrel paired with a reflex-style silencer. As in, it has a suppressor with a body design that goes back over the barrel (OTB) to increase internal volume. Maxim then marries this to an SDX receiver set, and covers up most of the business with their two-piece Ledge handguard. This results in what appears to be a rifle of “normal” length, albeit with a bit of silencer sticking out. The silencer portion of the RFLX is longer than the barrel — this comical effect is pronounced when the handguard is removed. The front end of the RFLX silencer itself is essentially a Maxim Defense M-Core DS silencer with their proprietary OTB rear attached, but specifically tuned to the barrel length and caliber. When viewed with the handguard off and out of context, the effect is quite comical — it looks like a huge 1980s Ciener silencer mounted to a little baby barrel. If you’re the type of person who doesn’t care about the external OEM finish on your rifle — maybe you should be. Not because it matters regarding the physical function of the rifle (everything should work these days, in a world of modern machines and engineering), but because it shows how much time and care was taken at the factory while it was being made. And as we’ve come to expect from Maxim Defense, every part of the SDX RFLX is meticulously clean. The machining is smooth with no toolmarks, and the anodizing is thick and even. The story continues with the controls and internals. The bolt carrier has an integral gas key — no worries about staking or fasteners at all. The charging handle is the ambidextrous Radian Raptor slimline SD, its shaft ported to aid gas venting. Rounding out exterior controls are swappable ambi Radian selector levers, an ambi magazine release, and ALG Combat Trigger. The gas key is integral to the bolt carrier — nothing to stake, nothing to lose There are a few variations of the SDX RFLX to choose from. They can be black or arid, SBR or “pistol,” with stock/brace options for each like a Maxim CQB stock or Magpul CTR. Given that the overall length is closer to a carbine than a PDW, here we went with a carbine tube and CTR instead of a shorty Maxim Defense stock. INTEGRATED, NOT INTEGRAL The RFLX isn’t a rifle with an integral silencer, it’s a rifle with an integrated silencer. There are just a few letters changed between the two terms, but it’s far from a distinction without a difference. Integral means built-in. Crucial. Integral silencers are typically permanently attached to the host, often the baffles are machined right into the barrel itself, with a long outer sleeve to house a massive gas expansion chamber. You’ll sometimes see gas bleed holes drilled into the barrels, trading some velocity for better sound suppression. (Noteworthy examples include the MP5SD, De Lisle Carbine, and the Nazi-snuffing OSS HD Military.) The EOTech OGL and SureFire pair perfectly, each controlled by the same dual remote switch. Integrated means joined. Two or more units meshing to make a larger system. Though the silencer module can be removed from the SDX RFLX, it was engineered and designed from the outset to always run suppressed with its dedicated suppressor. You can think of integral silencers as closed systems, integrated silencers as open systems. Integral silencers invariably have much more internal volume than a standard screw-on detachable suppressor. This helps lower pressure and increase overall performance, which is especially helpful with older 20th-century baffle designs. But the main reason you’d want an integral suppressor versus an integrated design isn’t because of performance but because of American regulations — you can get away with just having one tax stamp instead of two, and also travel interstate without pre-approval from the BATFE. But this article is being written in 2026 — you can get a brace instead of an SBR to avoid travel woes, and tax stamps cost a whole $0 and take about two weeks. An integrated silencer can be removed for cleaning and is easily serviced, swapped, or upgraded. And speaking on the SDX RFLX in particular, as the suppressor is an over-the-barrel design it still gives much more internal volume to the blast chamber like you’d see with an integral. Even though the silencer on the RFLX can be removed, you probably shouldn’t be taking it off unless something has gone wrong. It takes a lot of ammunition to foul up one of these cans enough to adversely affect the sound; it’s best to think of removal more like an armorer’s option than anything else. OUTFITTING Even though Maxim’s two-piece Ledge handguard has more space inside than most M-LOK forends in order to accommodate the Rubenesque 1.75-inch outer diameter silencer, attaching M-LOK hardware can sometimes be a real pain. Thankfully, the handguard is simple to disassemble. Three fasteners hold the front of the forend on, two of them being the QD sling cups themselves — a slick feature. The front piece of the handguard comes right off, but if you want to remove the rear for some reason, you’ll first have to unscrew the silencer. Regarding optics, because this is a .300 BLK rifle, a red dot fits the bill perfectly — and there’s a lot to love about the bigassed window of an EOTech. The EXPS3 DCR is night vision compatible, the new Danger Close Reticle is great at close and middle distance, and the tan looks like it was made for Maxim’s arid colorway. Also from EOTech is the newly released OGL C, On-Gun Laser Commercial Power. It’s an “eye safe” version of their military/LEO OGL, complete with optically slaved IR/vis lasers, a fantastic focusable IR illuminator, and good switchology. For a white light, we went with a SureFire M600V on an Arisaka mount with a SR07-D-IT tape switch to activate both the WML and OGL. The IR option of the SureFire isn’t needed here, but hey — it doesn’t exactly hurt either. LOOSE ROUNDS As we mentioned right at the beginning, on the range this one is a smooth shooter. In terms of sound, while the decibel meter isn’t everything (it’s best to think of it like one attribute rather than the whole kahuna) with subs you’re only looking at 129dB. 8.5 inches is in the Goldilocks zone of .300BLK barrel lengths, at least when you’re doing .300BLK things. If you’re wanting to shoot quietly at longer ranges, you should be looking at other calibers. To that end, it would be great to see the RFLX line expanded to include additional chamberings. Something that made Maxim Defense a market standout when they began producing rifles in the first place was making a 7.62×39 AR that actually worked, and a RFLX in the same would be welcomed. And doing it in hard mode? Managing the pressures and thermal mitigation of 5.56mm or 6ARC. Sure, you could probably put something like this together yourself — hell, Maxim Defense will even sell you most of the parts — but this isn’t a gun for someone who wants to switch around silencers or wants to fiddle, but for someone who wants everything to be nice and work right out of the box. .300BLK suppressed is like cheating already — it’s a round that was literally tailor-made to shoot from a silencer. So, if a company is going to make an integral integrated rifle it’s got to be good. Good news for Maxim Defense, this one is excellent. Why you can trust RECOIL Since our founding in 2012, RECOIL remains the premier firearms lifestyle publication for the modern shooting enthusiast. We deliver cutting-edge coverage of guns, gear, accessories and technology. We go beyond basic reviews, providing no B.S. buyer’s guides, hands-on testing and expert analysis on everything from firearms and survival equipment to watches and vehicles. 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