Mossberg 590M 12 Gauge 18.5″ Tungsten Gray, Magpul SGA, 10+1
Video review
Expert review
About this product
What is the Mossberg 590M 12 Gauge 18.5″ Tungsten Gray, Magpul SGA, 10+1? It's a magazine-fed, pump-action shotgun engineered to replace traditional tube-fed platforms with a detachable, 10-round polymer box magazine system while retaining the proven Mossberg 500-series action and controls. This configuration features an 18.5-inch barrel with a Tungsten Gray Cerakote finish, a Magpul SGA stock for enhanced ergonomics, and a factory-drilled-and-tapped receiver for optic mounting. My focus here is the mechanical execution and the specific regulatory and practical compromises inherent in a high-capacity, semi-tactical pump gun.
What is the Mossberg 590M used for?
The 590M is designed for tactical training, home defense, and as a duty shotgun where users prioritize swift reloads and precise ammunition management over pure capacity. The detachable magazine system allows you to transition between different loads—like buckshot to slugs—by swapping magazines in under 5 seconds, a key advantage over traditional tube-fed shotguns like the Mossberg 590A1. With its 18.5-inch barrel, it maintains a 34.5-inch overall length, making it maneuverable in confined spaces while the 10+1 capacity provides a substantial combat load without the bulk of extended tubes.
How does the Mossberg 590M compare to the Stevens 555 Sporting O/U?
The Mossberg 590M is a mechanically simpler, more durable tactical shotgun, whereas the Stevens 555 Sporting is a break-action, over/under shotgun built for clay target sports. The 590M, with its 10+1 capacity and pump action, offers higher volume and faster follow-up shots for defensive use, while the Stevens 555 Sporting 12 Gauge excels at controlled, precise pairs on the trap or skeet field due to its twin-choke system and lighter 6.8-pound weight. The Mossberg is the clear choice for defensive scenarios or force-on-force training; for pure recreational clays, the smooth-shooting balance of the Stevens 555 is superior.
What does it weigh and what are the dimensions?
Unloaded, the 590M in this configuration weighs 7.1 pounds, which is 0.8 pounds heavier than a standard 590A1 due to the magazine well and reinforced housing. The barrel is precisely 18.5 inches long, with an overall length of 34.5 inches from buttpad to muzzle. The length of pull on the Magpul SGA stock is adjustable from approximately 12.5 inches to 14.5 inches using included spacers, accommodating most shooters from 5'8" to over 6'2". These dimensions keep it under the legal minimum for a Title II Short-Barreled Shotgun (SBS), an important NFA consideration.
Who is this NOT for?
This shotgun is not for enthusiasts seeking a lightweight, traditional hunting platform or a dedicated competition gun. The magazine system adds complexity, bulk, and weight over a plain 590, making it less ideal for carrying long distances in the field. It's also a poor choice for someone whose primary use is waterfowl or upland bird hunting, where a lighter, faster-handling semi-auto like a Beretta A300 would be far more appropriate. If your needs are purely recreational clays or hunting, consider the purpose-built sporting options in our lineup.
What's in the box?
The factory package includes the 590M shotgun, one 10-round polymer magazine, Magpul SGA stock installation hardware and spacers for length-of-pull adjustment, the factory-installed fiber optic front sight, and the standard Mossberg owner's manual. Notably, it does *not* come with a magazine loader, which is a nearly essential $25-$35 aftermarket purchase, or with any additional chokes—the fixed cylinder bore choke is permanent. Expect to spend an additional 20 minutes properly installing the Magpul SGA stock and torquing the action screws to spec.
Is the Mossberg 590M worth it at $784.99?
At $784.99, the 590M represents a premium over a standard 590A1, which typically sells for around $650, with that $135 premium buying you the magazine-fed system and the Magpul SGA stock. For a shooter who specifically wants the reload speed and ammo management advantages of a detachable magazine on a pump-action platform, it is absolutely worth the cost, as aftermarket retrofits are unreliable. However, if you are ambivalent about magazine feeding and prefer the simpler, slimmer profile of a tube-fed gun, the standard 590A1 is the better financial and functional value.
Specs at a glance
Pros & cons
What works
- 10+1 capacity via detachable magazine — reloads in under 5 seconds versus 15+ seconds for a tube.
- Magpul SGA stock provides a 2-inch adjustable length of pull (12.5" to 14.5") for improved fit.
- Drilled and tapped receiver accepts a Picatinny rail (sold separately) for red dot or optic mounting.
- Tungsten Gray Cerakote finish on the barrel resists corrosion far better than standard blued steel.
Trade-offs
- Fixed cylinder bore choke limits patterning versatility — no option for tighter chokes without a new barrel.
- Weighs 7.1 lbs unloaded — 0.8 lbs heavier than a standard tube-fed 590A1, noticeable during extended handling.
- Polymer magazines are proprietary and expensive — additional 10-round mags cost $45-$55 each.
- No magazine loader included — a necessary $25-$35 aftermarket purchase for loading without thumb fatigue.
Key attributes
| upc | 015813502207 |
| manufacturer | Mossberg |
| manufacturer part number | 50220 |
| barrel length | 18.50" |
| caliber/gauge | 12 Gauge |
| capacity | 10 + 1 |
Frequently asked questions
- Does this work with standard Mossberg 500/590 barrels?
- No, it does not. The 590M receiver is machined specifically for the magazine feed system, requiring a dedicated 590M barrel. Standard 500/590 barrels will not fit due to interference with the extended magazine well. Confine barrel swaps to Mossberg's official 590M-specific offerings.
- Is it compatible with Benelli M4 accessories?
- Almost none. The 590M is built on the Mossberg 500 action, which shares zero parts interchangeability with the Benelli M4's inertia-driven system. Magazines, stocks, and forends are completely proprietary to the 590M platform. Sights and optics mounted via the receiver's Picatinny rail are the only universal items.
- How long does shipping to an FFL take?
- For in-stock items, Ironclad Armory processes and ships within 2 business days. Transit time varies by carrier and location, but continental US delivery to your selected FFL dealer typically takes 3-7 additional business days. You must contact your FFL in advance to provide their license for shipment.
- Does this come with a threaded barrel for chokes?
- No. The 18.5-inch barrel on this model has a fixed, non-removable cylinder bore choke (approximately 0.730" constriction). It is not threaded for choke tubes. For a model that accepts chokes, you would need to source a separate 590M barrel from Mossberg, usually in a longer hunting or tactical length.