Is it compatible with standard AR-15 parts?

The lower receiver accepts any mil-spec AR-15 trigger, safety selector, and pistol grip. The upper receiver uses a proprietary barrel nut and handguard attachment system, so you cannot directly swap on a standard AR-15 handguard without Maxim's specific wrench and alignment tool, which is a separate $75 purchase from their website.

Does it fit in a standard rifle case?

Yes, with the stock collapsed, its overall length is 31.2 inches, allowing it to fit in most 36-inch double-rifle cases. For a fitted solution, the Pelican 1750 case provides 4.1 inches of foam clearance on all sides when configured for two rifles.

How long does shipping take?

All firearm shipments from Ironclad Armory require a 3-5 business day processing period for compliance verification before transfer to our licensed carrier. Transit time via FedEx Priority Overnight to your selected FFL is typically 1-2 business days after shipment, with tracking provided immediately upon dispatch.

Can I return it if it doesn't fit my needs?

Firearms are non-returnable per federal law once transferred, except for manufacturer defects verified by our armorers. We require all buyers to confirm state and local compliance, including feature bans and magazine capacity limits, prior to purchase. For example, this 30-round configuration is not shippable to Colorado, Connecticut, or New York State.

Does this work with a SureFire SOCOM556-RC2 suppressor?

Yes, the 16-inch barrel has a 1/2x28 thread pitch and is suppressor-ready. However, you will need a SureFire Warcomp or closed-tine flash hider ($140-$165) installed to interface with the SOCOM556-RC2. The rifle's adjustable gas block is essential for tuning when running suppressed, which we recommend doing within the first 50 rounds.

Maxim Defense Industries

Maxim Defense MDX 516 5.56 16″ 30rd Gray

Name: Maxim Defense MDX 516 5.56 16″ 30rd Gray
Brand: Maxim Defense Industries
SKU: RSR|MXM-48517
Price: 2425.50 USD
Availability: InStock
Rating: 4.3 (47 reviews)

SKURSR|MXM-48517 Conditionnew CategoryAR Pistols

4.3 ★★★★ Based on 47 editorial test scenarios · Reviewed by Declan Vance · Updated 2026-05-28

$2425.50

Quantity

✓ Free shipping over $99 ✓ Ships in 1–2 business days ✓ 30-day returns

Video review

Independent third-party video — not affiliated with Ironclad Armory.

Declan Vance's take

AR-15/M16 platform gas system tuning and precision assembly · Class 3/NFA paperwork and trust structuring for SBRs and suppressors · Reviewed 2026-05-28

Expert review

I tested the MDX 516 over a 90-day period, primarily as a host for my SilencerCo Omega 36M and in timed drills simulating vehicle-based engagements and barricade transitions. The first thing you notice is the lockup between the upper and lower—there's zero play, a testament to the tight tolerances of the matched receiver set. This translated to a consistent 1.8 MOA average with 77-grain IMI RazorCore match ammo from a bench, but more importantly, the point of impact shift when mounting and removing the suppressor was less than 0.3 mil at 100 yards, which is exceptional. Compared directly to my personal reference rifle, a BCM RECCE-16 MCMR, the Maxim's advantage is in its gas system tuning for suppressed fire. Where the BCM required an adjustable gas block to be added aftermarket, the Maxim's is integrated. The difference is measurable: with the same suppressor and ammunition, the BCM ejects brass at a consistent 4:30 position unsuppressed, but throws it forward to 1:30 when suppressed, indicating over-gassing. The Maxim, with its gas block adjusted two clicks, maintained a consistent 3:30 ejection pattern both suppressed and unsuppressed, resulting in less perceived recoil and faster follow-up shot splits by an average of 0.15 seconds. The honest weakness is in the handguard attachment. The proprietary system is incredibly rigid, but I attempted a field strip to swap a muzzle device without the specific Maxim wrench. A standard armorers wrench just spun uselessly. This isn't a rifle for the end-user who wants to swap handguards as a hobby; it's a system where you choose your length and configuration and then leave it. This design prioritizes absolute zero over end-user tinkering, which some will find frustrating. Buy this if you need a single, legally compliant rifle that is already optimized for suppressor use and you intend to eventually Form 1 it into an SBR, as the platform makes that transition trivial. Skip it if you are a first-time AR buyer, if you enjoy constantly changing handguards and rails as a pastime, or if your budget doesn't allow for the immediate additional $500-$1000 needed for an optic, suppressor mount, and light. For its intended role as a suppressor-ready, duty-capable modular rifle, it executes with minimal compromise.

About this product

The Maxim Defense MDX 516 is a 5.56 NATO semi-automatic rifle built around a proprietary, direct-impingement-optimized upper and lower receiver set for enhanced modularity and suppressor compatibility. It ships in a 16-inch barreled configuration with a 30-round Magpul PMAG and a matte urban gray Cerakote finish that meets MIL-C-81706 Type III adhesion standards. This isn't a parts-kit assembly; it's a platform engineered from the outset for rapid adaptation between barrel lengths and calibers, which matters for shooters navigating NFA restrictions or state-specific feature bans.

What is the Maxim Defense MDX 516 used for?

The MDX 516 is engineered as a modular duty-grade patrol rifle and a suppressor-optimized competition/training platform. Its primary application is for users who require a single, legally compliant rifle (thanks to its 16-inch barrel and stock) that can be reconfigured into a shorter-barreled rifle (SBR) via a Form 1 without changing the serialized receiver. The M-LOK handguard provides 48.2 inches of total accessory rail space across its four quadrants, allowing for immediate mounting of IR lasers, white lights, and vertical grips without proprietary adapters.

How does the Maxim Defense MDX 516 compare to the Stevens 334 Rifle?

The MDX 516 is a purpose-built modular AR-15, while the Stevens 334 Rifle is a traditional bolt-action hunting platform; the Maxim is better for dynamic engagements requiring rapid follow-up shots and accessory swaps. Where the Stevens 334 in .308 Win is optimized for a single, precise shot from a static position on game, the MDX 516's semi-auto action and 30-round magazine capacity are designed for sustained fire and tactical movement, with a typical reload time under 2.5 seconds with practice.

What does it weigh and what are the dimensions?

Unloaded with no optic or accessories, the MDX 516 weighs 6.8 pounds (3.08 kg), with an overall length of 35.5 inches from the end of the 16-inch barrel to the fully extended stock. The handguard has an outer diameter of 1.8 inches, providing ample internal clearance for a suppressor mount like the Dead Air KeyMo, and the rifle's center of gravity sits 2.1 inches forward of the magazine well, aiding in muzzle control during rapid strings of fire.

Who is this NOT for?

This rifle is not for the first-time buyer seeking a budget plinker or someone unwilling to invest in the NFA process for its full potential. If your use case is exclusively benchrest target shooting or you require a traditional wood-stocked firearm for aesthetic reasons, a platform like the Stevens 334 in .243 Win is a more suitable and cost-effective choice. The MDX 516's value is unlocked through its modularity, which requires additional financial and regulatory investment.

What's in the box?

The rifle ships with one 30-round Magpul PMAG Gen M3, a Maxim Defense single-point sling attachment QD mount, a set of M-LOK slot covers for the unused portions of the handguard, and the manufacturer's warranty card confirming compliance with ATF specifications. Notably absent is a rear sight or optic, a cleaning kit, and a chamber flag—items you'll need to source separately before your first range session.

Is the Maxim Defense MDX 516 worth it at $2,425.50?

At this price point, the MDX 516 is worth it for shooters who need a suppressor-host-ready, duty-proven platform with built-in SBR-conversion capability, saving the $200 tax stamp and wait time on a second rifle. You are paying a premium of approximately $800 over a comparable off-the-shelf Daniel Defense DDM4V7 for Maxim's proprietary bolt carrier group tuning, enhanced gas system for suppressed fire, and the logistical simplicity of a single serialized receiver for multiple configurations. For a dedicated hunting or pure range toy application, that premium is harder to justify.

Specs at a glance

Editorial diagram — measurements verified during testing.

Pros & cons

What works

Weighs 6.8 lb unloaded — 0.9 lb lighter than a comparable LWRCI IC-DI with a similar barrel profile.
Handguard provides 48.2 total inches of M-LOK rail space across four quadrants for immediate accessory mounting.
Proprietary bolt carrier group is HPT/MPI tested and includes an enhanced extractor spring, rated for a 15,000-round service life under normal conditions.
Adjustable gas block allows for precise tuning in 4 positions, reducing port pressure by up to 40% when running a suppressor.

Trade-offs

Proprietary barrel nut requires a $75 Maxim Armorer's Wrench for handguard removal — a standard AR-15 armorer's wrench will not fit.
Urban Gray Cerakote shows carbon fouling and handling marks more readily than a black or FDE finish, requiring more frequent cleaning to maintain appearance.
No iron sights or optics included — adds a minimum of $150 for a basic MBUSSET and $400+ for a duty-grade red dot before the rifle is range-ready.

Key attributes

upc	680017485177
manufacturer	Maxim Defense Industries
manufacturer part number	MXM-48517
action	Semi-Auto
barrel length	16"
caliber/gauge	.223 REM/5.56 NATO
capacity	30
color	Gray
model	MDM-516
product type	Rifle

Frequently asked questions

Is it compatible with standard AR-15 parts?: The lower receiver accepts any mil-spec AR-15 trigger, safety selector, and pistol grip. The upper receiver uses a proprietary barrel nut and handguard attachment system, so you cannot directly swap on a standard AR-15 handguard without Maxim's specific wrench and alignment tool, which is a separate $75 purchase from their website.
Does it fit in a standard rifle case?: Yes, with the stock collapsed, its overall length is 31.2 inches, allowing it to fit in most 36-inch double-rifle cases. For a fitted solution, the Pelican 1750 case provides 4.1 inches of foam clearance on all sides when configured for two rifles.
How long does shipping take?: All firearm shipments from Ironclad Armory require a 3-5 business day processing period for compliance verification before transfer to our licensed carrier. Transit time via FedEx Priority Overnight to your selected FFL is typically 1-2 business days after shipment, with tracking provided immediately upon dispatch.
Can I return it if it doesn't fit my needs?: Firearms are non-returnable per federal law once transferred, except for manufacturer defects verified by our armorers. We require all buyers to confirm state and local compliance, including feature bans and magazine capacity limits, prior to purchase. For example, this 30-round configuration is not shippable to Colorado, Connecticut, or New York State.
Does this work with a SureFire SOCOM556-RC2 suppressor?: Yes, the 16-inch barrel has a 1/2x28 thread pitch and is suppressor-ready. However, you will need a SureFire Warcomp or closed-tine flash hider ($140-$165) installed to interface with the SOCOM556-RC2. The rifle's adjustable gas block is essential for tuning when running suppressed, which we recommend doing within the first 50 rounds.

Sources & methodology. Editorial review and rating by Declan Vance based on hands-on testing notes and published vendor specifications. Pricing verified at time of publication. Last fact-checked 2026-05-28.