Maxim Defense SDX:510

By: Dave Bahde

Super-tuned and ready to run hard from the factory

Integration

Rifle suppression, especially with the 5.56mm cartridge, has long been nothing more than a series of compromises. Having been using, testing, and building rifles and the suppressors that go with them for three decades, I have seen almost everything. Most everything has been developed with a focus on one issue, at the expense of others. Quiet suppressors tended to have more back pressure and gassed you out. Low backpressure designs were loud.   More importantly, they all worked differently on each rifle, as rifles were a compromise in and of themselves. It has always been a balancing act at each level, often revolving around versatility and the market, not the product itself. That has started to change in the last few years, with proper integration becoming the key focus. Rather than making separate systems with their own set of compromises to reach a broad market, systems are built together to create the best tool for a particular job or end user. Maxim Defense has been one of the few companies to adopt this philosophy and has done very well with it.

Maxim SDX:510

Maxim Defense has been building a reputation for years as one of the most reliable and rugged AR manufacturers on the market.   Starting with forged receivers, they are built to be strong, light, and compatible with mil-spec parts. Internals are basic, proven, and manufactured from the highest quality materials. The trigger is the highly proven ALG Advanced Combat Trigger (ACT). Machined to tight tolerances and coated using their HardLubing, it takes the “mil-spec” trigger to a different level. Clean, crisp, and predictable, it provides a repeatable 5.5-lb pull while meeting most, if not all, agency requirements for duty use. The upper receiver uses the HK416-style top rail; taller and stronger, it only enhances strength and longevity. The handguard is built for strength as well and includes both QD swivel and M-LOK compatibility. Beneath the handguard, a 10.3-inch 4150 CM Nitride barrel built with strength, reliability, longevity, and downrange precision in mind. While the SDX:510 can be ordered with a standard collapsible stock (B5 Bravo), our test rifle wears the optional CQB stock. All metal, the CQB stock collapses into a much more compact profile.

The suppressor portion, which is part of the package, is the company’s DSX-D — an extreme use model with no barrel restrictions and built from 17-4 Stainless (core) with a Grade 5 titanium tube that can be removed for cleaning. While direct-thread for easy removal, the rifle and suppressor are purpose-built to work together, focusing on clean operation, reliable functioning, and the least amount of added recoil or excess gas. While not “integral” in the traditional sense of being permanently attached, they are designed from the ground up to work together.

Range Time

My test rifle was equipped with a Trijicon MRO SD red-dot optic and 3X magnifier using a swing-away mount. Troy Industries flip-up BUIS designed for the HK top rail were used, providing a lower-third co-witness. Shorter mounts can provide an absolute co-witness if needed.

My biggest initial question before live fire was, is it truly “integrated”, or in my mind, tuned properly as a system? Some of the most rugged and proven rifles out there are harsh recoiling gas-making machines when a suppressor is added. They can be tuned to work with or without a suppressor, but generally it’s a “one or the other” proposition. Maxim has really done their homework on this rifle; it runs as well, or better, than any AR I’ve used that was tuned specifically for suppressor use. Felt recoil and gas directed back at my face was minimal, and in many cases, less than some of my over-gassed ARs without a suppressor. Brass ejection was excellent and consistent. Even after a couple of hundred rounds, the action was not caked in residue, and while residue was present on the magazines, it was not excessive.

Reliability was excellent with everything from 55-grain practice fodder to the most accurate of the 77-grain match rounds. Hotter rounds had a tad more recoil, but that is to be expected. With not enough time for me to prove durability, other Maxim rifles have done exceedingly well over 10K plus testing. Compared in “feel” to my LMT and LWRCI rifle, both with years of abuse and high round counts, this SDX:510 provides the same feeling. Lightweight? Nope, but not overly heavy either — it just feels robust. The charging handle and safety selector are both from Radian Weapons and are both ambidextrous. The magazine release is also ambidextrous, this one being the Marine Corps-proven Norgon LLC Ambi-Catch.

Downrange precision was very solid, with my best group at 100 yards measuring around an inch using Black Hills Ammunition’s 77-grain MK 262 Mod 1-C — the military precision round developed for the US Navy in 1999. Black Hills 77 TMK was produced essentially the same performance — spicy for sure, but incredibly accurate. Another round it really liked was Double Tap Ammunition’s Colt Defense 62-grain SC-HP solid-copper defense round, along with its matching 62-grain NM FMJ training round. The Double Tap loads were the softest-shooting of the bunch and some of my favorites; being able to use the FMJ for practice with a nearly identical POA/POA to the solid-copper duty round is a huge bonus.

Other Considerations

I’m personally not a big fan of the CQB stock, but it remains pretty popular. The CQB makes it easier to fit in some of the less obvious rifle cases, but not as well as a folder would. If I were ordering an SDX:510, it would end up with a standard collapsible stock. The difference in length and weight between the two is not that huge, and I would prioritize the comfort of a standard stock. Your mileage may vary.

The handguard is larger than the “skinny” versions that have become so popular, but it’s by design to envelope the rear portion of the suppressor. It’s not an issue for me, and in fact, it’s my preference these days, but some will find it overly big. Its larger diameter means it’s far less likely to break at the receiver when adding light/laser enablers at the far front. Having seen this breakage on a couple of rifles over the years, skinny is not always better.

If you are looking for an uber-light comp gun with an oppressive brake, a thin handguard, and a touchy trigger, this is NOT the ticket. Designed as an integrated system to be used suppressed all the time, you feel like you are carrying a purpose-built rifle you would take to a real fight, not a contest.

Bottom Line

This test started with a bit of skepticism, given the rifle’s $3695.00 price tag (rifle and suppressor). After time on the range and conversations with some professional end-users with extensive time with Maxim Defense products, the SDX:510 lived up to its MSRP. Build quality is very high, and it’s apparent that it was all done with the mindset of creating a professional tool. Integration was absolutely as described by Maxim Defense, with the rifle and suppressor tuned as a unit, not just a rifle with a can attached. As a huge fan of the 10.5-ish” barrel length, the SDX:510 is the perfect size for professional use when suppressed. In the end, this rifle is as billed — a rugged, reliable, and integrated system that’s suitable for the harshest conditions right out of the box. See the SDX:510 at your nearest dealer, or for more information, contact Maxim Defense; Tel. (239) 580-7800; E-mail: [email protected]; Web: www.maximdefense.com

Action:                                    Semi-auto, direct-impingement

Caliber                                   5.56x45mm / .223 Rem.

Barrel Length                         10.3 inches

OAL:                                     31.5 inches extended

Weight:                                  7 pounds, 15 ounces

Capacity                                30 rounds (Accepts standard AR magazines)

MSRP                                    $3695.00