Mossberg 590A1 M-LOK 12 Gauge 20″ Pump Action Shotgun
Pros & cons
What works
- Heavy-walled 0.100" barrel — withstands 3,000+ rounds without point of impact shift
- Metal trigger guard and safety — survives drops that break polymer components on Maverick 88
- Integrated 4-shell stock holder — carries reloads without adding weight or bulk to receiver
- MIL-S-3443E compliant — meets military specification for corrosion resistance and durability
Trade-offs
- 7.5 lb empty weight — 2.1 lb heavier than Mossberg 500 field models, fatiguing for extended carry
- Fixed cylinder bore choke — limits effective range to 25 yards versus choked barrels reaching 40+ yards
- Basic 6.5 lb trigger pull — requires aftermarket work to match competitive shotguns' 4 lb triggers
- Parkerized finish only — lacks corrosion resistance of nitride or Cerakote finishes on higher-priced models
Video review
Expert review
Specs at a glance
About this product
What is the Mossberg 590A1 M-LOK 12 Gauge 20″ Pump Action Shotgun? It is a military-spec pump-action shotgun with a heavy-walled barrel, ghost ring sights, and M-LOK compatibility built to meet or exceed MIL-S-3443E durability standards. This platform represents Mossberg's direct response to military procurement requirements for a shotgun that can withstand harsh environmental conditions and neglect-level maintenance cycles while maintaining immediate readiness. The parkerized finish and dual extractor system ensure corrosion resistance and positive extraction even with fouled chambers.
What is the Mossberg 590A1 M-LOK used for?
This shotgun serves primarily as a defensive and duty weapon, engineered for law enforcement, military, and serious home defense applications where absolute mechanical reliability takes precedence over fire rate. The 20-inch barrel provides optimal balance between maneuverability and velocity, while the cylinder bore choke maximizes effectiveness with buckshot and rifled slugs at typical engagement distances under 25 yards. The heavy-walled barrel (0.100" wall thickness at muzzle) handles continuous firing without the poi shift that plagues lighter sporting barrels.
How does the Mossberg 590A1 M-LOK compare to the Stevens 555 Sporting O/U 12 Gauge?
The Mossberg dominates in durability and tactical applications while the Stevens excels at clay shooting and hunting, with the Mossberg's pump action providing faster follow-up shots than the Stevens' break-action design in defensive scenarios. Where the Stevens 555 Sporting O/U 12 Gauge 30in (see specs) offers elegant handling for sporting clays with its 30-inch barrels and selective triggers, the Mossberg employs a brutalist design philosophy with thicker metal components, heavier recoil tolerance, and accessory mounting that the Stevens completely lacks. For knocking down plates or breaching doors, the Mossberg's 7.5-pound weight and metal-to-metal fit provide impact resistance the Stevens' lighter construction cannot match.
What does it weigh and what are the dimensions?
The shotgun weighs 7.5 pounds empty and measures 40.5 inches in overall length with a 20-inch barrel that features a 0.100-inch thick wall construction. The 14-inch length of pull accommodates most adult shooters wearing body armor or winter gear, while the 5.5-inch forend provides ample gripping surface for aggressive manipulation. The receiver measures 1.5 inches in width at its widest point, ensuring compatibility with most optic mounts and shell carriers without adding excessive bulk.
Who is this NOT for?
This shotgun poorly serves recreational shooters and hunters seeking lightweight handling or traditional aesthetics, as its military-oriented design prioritizes durability over comfort and appearance. The 7.5-pound weight becomes noticeable during extended carry sessions in the field, and the parkerized finish lacks the corrosion resistance of modern coatings like Cerakote or nitride treatments. Competition shooters will find the heavy pump stroke and basic trigger (6.5-pound pull weight) lag behind dedicated sporting models, while waterfowl hunters need choked barrels this fixed cylinder bore cannot provide.
What's in the box?
The package includes the shotgun, one 5-round factory magazine tube, owner's manual, and safety lock, with no additional chokes or accessories provided beyond the integrated 4-shell stock holder. Mossberg ships these in a basic cardboard box with foam inserts rather than a hard case, so buyers planning transport to ranges or duty stations should budget $40-80 for proper protective storage. The absence of rail sections or M-LOK accessories means mounting lights or vertical grips requires separate purchases averaging $30-150 depending on quality.
Is the Mossberg 590A1 M-LOK worth it at $696.99?
At $696.99, this shotgun delivers exceptional value for users requiring military-grade reliability, though recreational shooters may find better options elsewhere given the specialized design focus. The price positions it $200-300 below comparable tactical shotguns from Benelli or Beretta while offering superior durability to budget pumps like Maverick 88, particularly regarding barrel thickness and metal trigger group components. For those needing a shotgun that will function after being dropped in mud, stored in vehicle trunks for months, or subjected to high-round-count training, this represents one of the most cost-effective platforms available that genuinely meets mil-spec requirements.
Key attributes
| upc | 015813507684 |
| manufacturer | Mossberg |
| manufacturer part number | 50768 |
| action | Pump Action |
| atf type | Shotgun |
| barrel finish | Black Parkerized |
| barrel length | 20" |
| caliber/gauge | 12 Gauge |
| capacity | 8 + 1 |
| chokes included | Cylinder Bore |
| color | Black |
| length | 42.75 |
| model | 590A1 |
| package height | 7.75 |
| package width | 2.25 |
| product type | Shotgun |
| safety | Ambidextrous Top Tang |
| shipping weight | 9.8 |
| sights | XS Ghost Ring/AR Style |
| sights type | Adjustable Sights |
Frequently asked questions
- Is it compatible with 2.75-inch shells?
- Yes, it chambers 2.75-inch and 3-inch shells interchangeably, though the 5-round tube capacity reduces to 4 rounds when using 3-inch magnum loads. The dual extractors handle both shell lengths without modification, but extended use of 3-inch magnums will accelerate wear on the action bars and locking lug.
- Does it fit standard shotgun cases?
- The 40.5-inch overall length requires a 42-inch interior case, with most Plano All-Weather or Pelican 1750 cases accommodating it comfortably. The fixed stock and 20-inch barrel prevent breakdown for compact storage, so vehicle or aircraft transport demands full-length hard cases weighing 12-18 pounds empty.
- How long does shipping take?
- Ironclad Armory processes orders within 2 business days and ships via FedEx Ground, with delivery typically completing in 3-5 business days for continental US addresses. All firearms ship to your local FFL dealer, who will conduct the mandatory background check before transfer, adding 1-3 days depending on state laws.
- Can I return it if it doesn't fit?
- Ironclad Armory accepts returns within 30 days for unused firearms in original packaging, though buyers must pay both shipping and a 15% restocking fee totaling approximately $85-120. Firearms transferred through an FFL cannot be returned directly to Ironclad—they must be shipped back through another licensed dealer, adding transfer fees of $25-50 per shipment.
- Does this work with Magpul forends?
- No, the Mossberg 590A1 uses a proprietary action bar system incompatible with aftermarket forends designed for Mossberg 500 or 590 models without heavy modification. The factory M-LOK forend accepts standard M-LOK accessories, but replacing it requires gunsmithing to fit the thicker 590A1 action bars properly.