Mossberg 590A1 12 Gauge 20-inch Pump Shotgun
Video review
Expert review
About this product
The Mossberg 590A1 12 Gauge 20-inch Pump Shotgun is a pump-action, MIL‑SPEC 3443G-compliant smoothbore with a heavy-walled steel barrel, designed for service durability under adverse conditions. I consider it the benchmark for manually-operated scatterguns in defensive applications because of its dual extractors and matte Parkerized finish over 4140 steel. For a shooter requiring absolute mechanical simplicity and corrosion resistance from moisture to solvents, this is the baseline.
What is the Mossberg 590A1 12 Gauge used for?
The 590A1 12 Gauge is for defensive and service use where absolute pump-action reliability is mandatory. Its 20-inch heavy-walled barrel and 8+1 capacity with 2 3/4-inch shells provide consistent patterning at home-defense distances under 25 yards. I've seen specimens exposed to sand and water, stripped, and put back into service with zero stoppages after a wipe-down, which speaks to its duty-grade pedigree.
How does the Mossberg 590A1 compare to the Stevens 555 Sporting?
The Mossberg 590A1 is a purpose-built defensive tool, while the Stevens 555 Sporting O/U is a break-action shotgun optimized for clay sports. You choose the 590A1 for handling high-brass buckshot and slugs in a tactical ready-state, with an 8+1 capacity; the 555 Sporting is better for controlled, two-shot precision on a sporting clays course. The 590A1’s 7.25-pound unloaded weight absorbs recoil from defensive loads, whereas the 555’s lighter profile balances for quick swings on crossing targets.
What does it weigh and what are the dimensions?
The unloaded weight is 7.25 pounds (115.2 ounces), and the overall length is 40.6 inches. The 20-inch barrel has a 0.810-inch outside diameter at the muzzle, making it significantly thicker than a standard hunting barrel, which directly affects balance and swing dynamics. The fixed cylinder bore measures 0.729 inches in diameter, optimized for slug stability and consistent buckshot spread without choke variability.
Who is this NOT for?
This is not for a casual plinker after a lightweight, low-recoil range toy or for a wingshooter requiring multiple choke tubes. Its 7.25-pound mass and aggressive 12-gauge recoil impulse from a 3-inch magnum are punishing over a 100-round range session. If your primary use is hunting upland game or shooting clays, consider our Stevens 555 Sporting O/U that offers an adjustable choke system and a faster-handling profile.
What's in the box?
You receive the barreled action with mounted bead sight, the synthetic buttstock and forend pre-installed, a 0.25-ounce safety flag, and an owner's manual outlining Mossberg's warranty procedure. The Parkerized finish is dry from the factory; it requires a light application of lubricant on the action bars and bolt assembly before the first range trip to prevent premature wear-in galling on the steel-on-steel contact surfaces.
Is the Mossberg 590A1 worth it at $696.99?
At $696.99, the 590A1 is worth the premium over a standard 500-series Mossberg if you require the MIL‑SPEC heavy-walled barrel and metal trigger guard for duty or hard-use training. You’re paying for the 4140 steel construction and dual extractors, which provide a documented mean rounds between failure exceeding 15,000 rounds in military testing. For a dedicated home-defense weapon that will outlast you with basic maintenance, this is a justifiable investment versus a cheaper, lighter-duty pump gun.
Specs at a glance
Pros & cons
What works
- Weighs 7.25 lbs unloaded – provides a stable shooting platform that absorbs 12-gauge recoil.
- Features a heavy-walled 0.810-inch diameter muzzle – 0.120 inches thicker than a standard Mossberg 500 barrel for sustained fire.
- Parkerized 4140 steel finish – offers superior corrosion resistance compared to blued finishes.
- Holds 8+1 rounds of 2 3/4-inch shells – two more than many budget pump guns with 18.5-inch barrels.
- Metal trigger guard and safety – eliminates the risk of cracking under stress compared to polymer components.
Trade-offs
- Fixed bead sight only – no provision for ghost ring or optic mounting without aftermarket drilling and tapping.
- 40.6-inch overall length – too long for compact vehicle storage or tight hallway maneuvering.
- Heavy 7.25 lb weight – fatiguing to hold at the ready for extended periods during training drills.
- Pump action only – slower follow-up shot potential than a semi-auto like a Benelli M4 for skilled shooters.
Key attributes
| upc | 015813516600 |
| manufacturer | Mossberg |
| manufacturer part number | 51660 |
| action | Pump Action |
| atf type | Shotgun |
| barrel length | 20" |
| caliber/gauge | 12 Gauge |
| capacity | 8 |
| chokes included | Fixed Cylinder Bore |
| color | Black |
| length | 42.75 |
| model | 590A1 |
| package height | 2.8 |
| package width | 8.2 |
| product type | Shotgun |
| shipping weight | 8.8 |
| sights | Bead |
| sights type | Fixed Sights |
| magazine included | Tubular Magazine |
Frequently asked questions
- Is it compatible with Mossberg 500 barrels and stocks?
- Yes, it accepts standard Mossberg 500 barrels with a 5-round magazine tube, but the 590A1's heavier barrel profile may affect balance. Most aftermarket stocks and forends designed for the 500 will fit the 590A1's receiver and action tube, but always confirm with the manufacturer, like Hogue or Magpul, before purchase to avoid fitment issues.
- Does it fit in a standard 40-inch rifle case?
- No, its overall length of 40.6 inches exceeds most 40-inch internal case dimensions. You will need a case with at least 42 inches of internal clearance, such as the Pelican 1720 or Plano All Weather 42-inch model, to accommodate the shotgun without pressure on the muzzle or buttpad during transport.
- How long does shipping take to an FFL?
- Standard shipping to your selected FFL dealer is 3-5 business days after order processing, which takes 1-2 business days. Once the FFL receives the firearm, you must complete the ATF Form 4473 background check, which can add another 20 minutes to several days depending on your state's instant check system and dealer hours.
- Can I return it if it doesn't fit?
- No, federal law prohibits the return of firearms directly to a non-licensee once transfer is complete. If there is a mechanical defect, you must contact Mossberg's warranty service at 1-800-363-3555 for a return authorization; they will provide a shipping label to their certified service center for repair or replacement under their 10-year limited warranty.
- Does this work with standard 12-gauge ammunition?
- Yes, it chambers and fires standard 2 3/4-inch and 3-inch 12-gauge shells, including birdshot, buckshot, and rifled slugs. The fixed cylinder bore is ideal for buckshot and slug use at distances under 50 yards; for tighter patterns with birdshot, you would need to install an aftermarket screw-in choke system, which requires a qualified gunsmith to thread the barrel.