Mossberg 590RM Mag-Fed 12 Gauge 18.5″ Pump
About this product
What is the Mossberg 590RM Mag-Fed 12 Gauge 18.5″ Pump?
The Mossberg 590RM Mag-Fed 12 Gauge 18.5″ Pump is a Title I, non-NFA pump-action shotgun configured for detachable box magazine feeding and close-quarters security applications. It builds on the 590's established reliability by incorporating a magazine-fed system and an 18.5-inch barrel to navigate the 18-inch federal minimum without entering Short-Barreled Shotgun (SBS) territory. This configuration prioritizes rapid reload capability and modular accessory mounting over traditional tube-fed capacity.
What is the Mossberg 590RM used for?
The 590RM is engineered for static security, vehicle-based operations, and as a modular home-defense platform where magazine swaps outperform tube loading. Its primary function is delivering reliable 12-gauge terminal ballistics in a compact, magazine-fed package that maintains a legal 26.5-inch minimum overall length. The stand-off barrel prevents accidental muzzle contact with barriers, and the Picatinny rail accepts modern micro red-dot optics for rapid sight acquisition in low-light conditions.
How does the Mossberg 590RM compare to the Stevens 555 Sporting O/U?
The Mossberg 590RM is a dedicated tactical pump-action, while the Stevens 555 Sporting O/U is a break-action sporting shotgun designed for clays and field use. The 590RM offers superior modularity and rapid reload capability via its 5-round detachable magazines, compared to the fixed, two-shell capacity of the Stevens 555. For defensive use, the 590RM's magazine system and accessory rail make it objectively better, but for recreational shooting, the Stevens' traditional handling and lighter weight are preferable.
What does it weigh and what are the dimensions?
Unloaded with the stock collapsed, the 590RM weighs 7.8 pounds. Its overall length is 38.5 inches with the stock fully extended, collapsing to 35.25 inches for storage. The 18.5-inch barrel provides a legal minimum overall length of 26.5 inches when the adjustable stock is in its shortest position, just 0.5 inches over the NFA's SBS threshold.
Who is this NOT for?
This is not a shotgun for hunters or recreational clay shooters. The magazine-fed system adds bulk and weight compared to traditional tube-fed shotguns like the Mossberg 500, and the 5-round capacity is lower than many tube-fed models. If your primary use is upland hunting or breaking clays, consider a dedicated sporting model like the Stevens 555 Sporting Compact 20ga 26″ for its lighter weight and faster handling.
What's in the box?
The package includes the shotgun with the 5-position adjustable stock installed, one 5-round polymer magazine, a cylinder-bore Accu-Choke tube, a choke tube wrench, and the owner's manual with a federal compliance sheet. Mossberg does not include a hard case, optics, or additional magazines—plan for those as separate purchases to make the platform operational.
Is the Mossberg 590RM worth it at $878.99?
At $878.99, the 590RM justifies its cost for users requiring a magazine-fed system who don't want to Form 1 an SBS or pay the premium for a semi-auto like the 930 SPX. You're paying for the integrated magazine well, adjustable stock, and Picatinny rail that would cost over $300 in aftermarket parts on a standard 590. For a purely defensive, no-frills pump-action, a standard Mossberg 500 Security model at around $450 is a more economical choice.
Specs at a glance
Video review
Pros & cons
What works
- 5-round detachable magazines enable reloads in under 4 seconds versus 10-15 seconds for tube-fed pumps.
- 7.8 lb weight balances well with the 18.5" barrel, reducing muzzle flip compared to lighter 6.5 lb defensive shotguns.
- Adjustable stock provides 3.25 inches of length-of-pull variance (12" to 15.25") for fit across body armor and different shooters.
Trade-offs
- Proprietary magazines cost $42 each and have limited third-party support versus ubiquitous tube-fed designs.
- No iron sights — requires an optic purchase and zeroing, adding $150+ to the total system cost.
- The parkerized finish shows wear quickly on high-contact areas like the receiver rails and magazine release.
Expert review
Key attributes
| upc | 015813502184 |
| manufacturer | Mossberg |
| manufacturer part number | 50218 |
| action | Pump Action |
| atf type | Shotgun |
| barrel length | 18.5" Breacher Barrel |
| caliber/gauge | 12 Gauge |
| capacity | 10 + 1 |
| chokes included | Cylinder Bore |
| color | PARKERIZED |
| length | 46.5000 |
| magazine included | 1 x 10-Round |
| model | 590 |
| number of magazines | 1 10 rd. |
| package height | 3.6 |
| package width | 9.1 |
| product type | Shotgun |
| shipping weight | 10.35 |
| sights | No Sights |
Frequently asked questions
- What magazines does the 590RM use?
- It uses Mossberg's proprietary 5-round polymer box magazines, part number 19585. These are not compatible with other Mossberg magazine-fed shotguns like the 590M, which uses a different magazine design and latch system.
- Is the barrel threaded for chokes?
- Yes, it uses Mossberg's Accu-Choke system with external threads. The included cylinder-bore choke tube provides a true cylinder constriction, but you can install any standard 12-gauge Accu-Choke tube for modified or improved cylinder patterns.
- Will a Magpul SGA stock fit this receiver?
- No, the 590RM uses a proprietary buffer tube and stock interface due to the magazine feed system. The included 5-position stock is not compatible with aftermarket stocks designed for standard 500/590 shotguns without significant modification.
- Can I mount a light on the forend?
- Not without modification. The factory forend lacks mounting points. You'll need an aftermarket M-LOK or Picatinny forend, or a clamp-on light mount that attaches to the magazine body, adding approximately 1.5 inches of width to the grip area.
- How long does Ironclad Armory take to ship firearms?
- Ironclad Armory processes and ships to your selected FFL within 2 business days after receiving a cleared payment and a copy of the FFL license. Transit time depends on your location and carrier, typically 3-7 business days for ground service.