Mossberg 590 Mariner 12 Gauge 20in Pump Shotgun
Pros & cons
What works
- Marinecote finish provides superior corrosion resistance, withstanding a 336-hour salt spray test per ASTM B117.
- Includes a pistol grip conversion kit, allowing a compact configuration change in under 15 minutes.
- 7-pound weight and 41-inch length manage 12-gauge recoil better than a 5.5-pound pistol-grip-only configuration.
Trade-offs
- Bead-only sight system is inadequate for precise defensive aiming past 25 yards; adding a rifle sight costs $75+.
- Synthetic forend lacks texture, becoming slick when wet—replacement with a textured Hogue costs $35.
- Package does not include the Allen wrench required for the pistol grip installation.
Video review
Expert review
Specs at a glance
About this product
The Mossberg 590 Mariner is a corrosion-resistant 12-gauge pump-action shotgun purpose-built for harsh marine and humid environments using a Marinecote finish and synthetic materials. It represents a specific engineering solution within Mossberg's 500 series, prioritizing material resilience over hunting ergonomics. Many shooters mistake it for a tactical shotgun, but its 20-inch barrel and fixed field stock place it firmly in a niche for boat or coastal defensive use.
What is the Mossberg 590 Mariner 12 Gauge 20in Pump Shotgun used for?
This Mariner is designed for marine-practical and defensive applications where saltwater corrosion is a primary concern. The Marinecote finish and synthetic components resist rust far better than blued steel, making it suitable for boat security, coastal homesteading, or use in high-humidity regions. It is not optimized for recreational clay shooting or upland bird hunting where weight distribution and swing matter more.
How does the Mossberg 590 Mariner compare to the Stevens 555 Sporting O/U 12 Gauge?
The 590 Mariner is objectively better for harsh, wet environments where a Stevens 555's walnut stock and blued barrels would rapidly degrade. The comparison is stark: the Stevens 555 Sporting O/U 12 Gauge 30in is a superior field gun for sporting clays, with its 30-inch barrels and walnut stock providing better balance and swing for a moving target. For raw durability in a defensive context, the Mariner's synthetic construction and protective finish give it a decisive advantage.
What does it weigh and what are the dimensions?
Unloaded, the shotgun weighs approximately 7 pounds and has an overall length of 41 inches from the buttplate to the muzzle crown. The 20-inch barrel is the functional minimum for legal Title I (non-NFA) configuration without requiring a tax stamp, and the 3-inch chamber accommodates a wide range of shell lengths. Compared to a more compact pistol-grip-only shotgun, this 41-inch length and 7-pound weight offer significantly more controllable recoil for follow-up shots.
Who is this NOT for?
This shotgun is not for the recreational clay shooter or upland bird hunter. Its 20-inch barrel and bead sight are suboptimal for breaking flying targets, and its weight-forward balance from the protective metal coatings doesn't swing like a traditional field gun. If your primary use is sport shooting, you are better served by our Stevens 555 Sporting O/U 12 Gauge with its more applicable features and better sporting ergonomics.
What's in the box?
The factory package includes the complete shotgun, an ambidextrous top-tang safety, a front bead sight, a pistol grip conversion kit, and a recoil pad. Unlike a bare-bones model, the inclusion of the conversion kit and pad allows the end user to configure the shotgun for a more compact, pistol-grip-only profile in about 15 minutes with a basic Allen wrench, which is not universally provided.
Is the Mossberg 590 Mariner worth it at $719.99?
Yes, if your operational environment specifically demands its corrosion-resistant features. At $719.99, you are paying a premium of roughly $150-$200 over a standard parkerized 500-series shotgun for the Marinecote finish and marine-specific components. For a shooter in the Southeast or on the Great Lakes where humidity and salt spray are constant threats, this premium is justified for the long-term maintenance savings and reliability assurance.
Key attributes
| upc | 015813502993 |
| manufacturer | Mossberg |
| manufacturer part number | 50299 |
| action | Pump Action |
| atf type | Shotgun |
| barrel finish | Silver Marinecote |
| barrel length | 20" |
| caliber/gauge | 12 Gauge |
| capacity | 8 |
| chokes included | Cylinder Bore |
| color | Silver |
| length | 42.6000 |
| model | 590 |
| package height | 7.75 |
| package width | 2.25 |
| product type | Shotgun |
| safety | Ambidextrous Top Tang |
| shipping weight | 8.75 |
| sights | Bead |
| sights type | Fixed Sights |
Frequently asked questions
- Is it compatible with standard Mossberg 500/590 accessories?
- Yes. The 590 Mariner uses the same forend attachment system and receiver threads as the standard 500/590 series. You can mount any aftermarket forend designed for the 500-series pump guns. However, note that the Marinecote finish may cause minor tolerance differences with some tight-fitting aftermarket parts.
- Does it fit standard 12-gauge shells?
- Yes. The shotgun is chambered for 2¾-inch and 3-inch 12-gauge shells. It will not accept 3½-inch magnum shells, which is standard for this action length. For optimal reliability, we recommend testing your specific defensive or target load, but it cycles Federal FliteControl 8-pellet 00 buck without issue.
- How long does shipping take?
- All firearms ship via Ironclad Armory's bonded carrier network within 3-5 business days after your background check clears with your chosen FFL. Transit time is typically 2-5 additional business days. The entire process from order to your FFL averages 7-12 business days, depending on your state's check system.
- Can I return it if it's defective?
- Yes, but only for manufacturer defects verified by our armorers. Ironclad Armory offers a 30-day inspection period for mechanical defects. The firearm must be unmodified and unfired, and returns must be initiated through your original point of purchase. We do not accept returns for buyer's remorse or improper accessory fitment.
- Does this work with a side-saddle shell carrier?
- Yes, but with a caveat. The synthetic stock is compatible with most adhesive-backed shell carriers. For a more permanent solution, the receiver is drilled and tapped to accept a Mesa Tactical or similar side-saddle that uses a mounting plate, requiring a #8-32 screw set, not included.