Mossberg 590A1 Pro 12 Gauge 18.5″ Magpul SGA
Pros & cons
What works
- Heavy-walled barrel is 0.125 inches thick — provides superior heat dissipation and rigidity vs. standard barrels.
- Marinecote finish offers 500+ hours of salt-spray corrosion resistance, crucial for coastal or humid environments.
- Magpul SGA stock adjusts length of pull across a 2-inch range with three spacers — allows precise fit for users in armor.
- Dual extractors and a steel-to-steel locking bolt provide redundant extraction, a key Mil-Spec reliability feature.
Trade-offs
- Weighs 7.9 lbs unloaded — over 1.5 lbs heavier than a standard 590, making sustained off-hand shooting more fatiguing.
- Fixed 6+1 magazine capacity cannot be extended — limits tactical flexibility compared to models with longer tubes.
- No sling swivel studs or QD points included on the stock — requires end-user installation of aftermarket solutions.
Video review
Expert review
Specs at a glance
About this product
The Mossberg 590A1 Pro 12 Gauge 18.5″ Magpul SGA is a service-grade, pump-action shotgun engineered for absolute reliability under demanding conditions. This configuration delivers professional-grade durability through features like a heavy-walled, corrosion-resistant barrel and an optic-ready receiver, packaged for the end-user who expects mechanical precision from a tool that must work. I’m Declan Vance, a former lead armorer and compliance specialist, and I’ll break down exactly where this shotgun fits—and doesn’t—in the current market, avoiding the typical sales fluff.
What is the Mossberg 590A1 Pro used for?
The Mossberg 590A1 Pro is used as a dedicated duty, home defense, and training platform where environmental resilience and mechanical fail-safety are non-negotiable. Its 18.5-inch heavy-walled barrel and Marinecote finish are built to handle moisture and neglect that would render a blued sporting shotgun useless. The ghost-ring and fiber-optic sight system, coupled with the optic-ready receiver footprint, allows for fast, repeatable target acquisition in low-light defensive scenarios, not just clay target games.
How does the Mossberg 590A1 Pro compare to the Stevens 555 Sporting?
The Mossberg 590A1 Pro is a purpose-built defensive tool, while a gun like the Stevens 555 Sporting O/U is a dedicated field and clays shotgun. The Mossberg is superior for hard-use reliability and rapid manipulation under stress, featuring a dual extractor system and a slide release independent of the safety. The Stevens is better for smooth swinging and precise shot placement on moving targets, with its lighter weight and double-trigger system. Choosing the Mossberg means prioritizing a 7+1 capacity tube magazine under a barrel that can handle high-volume, rapid fire.
What does it weigh and what are the dimensions?
This shotgun weighs 7.9 pounds unloaded and measures 38.5 inches in overall length. The heavy-walled barrel contributes significantly to this weight, adding about 0.8 pounds compared to a standard-profile barrel of the same length. The adjustable Magpul SGA stock allows a length of pull from 12.25 inches to 14.25 inches in 0.5-inch increments, a crucial fitment for shooters in body armor or for tailoring the gun to different household users.
Who is this NOT for?
This shotgun is not for the first-time shooter seeking an inexpensive, lightweight field gun for casual bird hunting. Its 7.9-pound weight and 18.5-inch barrel make it cumbersome for carrying all day in the woods compared to a lighter over/under like the Stevens 555 Sporting Compact. It’s also not ideal for pure competition clays shooting, where its shorter sight radius and defensive-oriented ghost-ring sights are a disadvantage versus a long-barreled sporting gun with a vent rib.
What’s in the box?
In the box, you will receive the assembled shotgun, three Magpul SGA stock spacers (for LOP adjustment), and the owner's manual. Mossberg does not include a chamber flag, a bore brush, or sling swivels as standard with this model. You will need to budget for a quality sling, a cleaning kit suitable for 12-gauge, and potentially an optic mount to utilize the pre-tapped receiver.
Is the Mossberg 590A1 Pro worth it at $1,161.99?
At $1,161.99, the Mossberg 590A1 Pro is worth it for the individual who requires a shotgun that meets or exceeds military-specification (Mil-Spec) standards for durability and plans to use it in austere or humid environments. You are paying a premium of roughly $300 over a standard 590 for the heavy-walled barrel, Marinecote corrosion protection, and the upgraded sighting system. If your use is limited to dry, indoor range sessions, a standard 590 model represents better value. For the professional user or the serious home defender, the overbuilt construction justifies the cost.
Key attributes
| upc | 015813507943 |
| manufacturer | Mossberg |
| manufacturer part number | 50794 |
| action | Pump Action |
| atf type | Shotgun |
| barrel length | 18.5" |
| caliber/gauge | 12 Gauge |
| capacity | 6 + 1 |
| chokes included | Cylinder Bore |
| package height | 2.6 |
| package width | 7.7 |
| product type | Shotgun |
| shipping weight | 9.8 |
| sights | Ghost Ring Sights |
| sights type | Adjustable Sights |
Frequently asked questions
- Is the receiver compatible with a red dot sight?
- Yes, the receiver is pre-drilled and tapped for an optic mount. Mossberg uses a #6-48 screw pattern. You will need to purchase a separate Picatinny rail or direct mount from a company like EGW (Evolution Gun Works) to install a micro red dot like a Trijicon RMR.
- Will this shotgun accept a magazine tube extension?
- No, the 590A1 Pro model with the 18.5-inch barrel has a fixed, 6-round magazine tube that is not designed for standard extensions. The barrel lug is permanently attached to the tube. To increase capacity, you would need to seek a different 590 model variant with a longer barrel and tube from the factory.
- Does it fit in a standard 40-inch rifle case?
- Yes, the shotgun's overall length of 38.5 inches allows it to fit comfortably in a standard 40-inch hard or soft rifle case with room for a couple of boxes of shells. For a case with thick foam, ensure the interior usable length is at least 39.5 inches to avoid compressing the stock.
- How long does shipping to an FFL take?
- Standard shipping to your selected Federal Firearms License (FFL) holder typically takes 3-7 business days from the time your order and FFL information are verified. All firearms must ship to a licensed dealer for the mandatory 4473 background check and transfer.