TriStar Cobra III Marine Pump 12 Gauge 18.5″ 5+1
Pros & cons
What works
- Chrome-lined bore and chamber — significantly extends service life in corrosive environments
- Weighs 6.2 lbs — manageable for its 36.5-inch defensive-oriented length
- Accepts Beretta/Benelli Mobil chokes — broad aftermarket support for patterning control
- Removable spring-assisted forearm — converts to standard pump action in under 2 minutes
Trade-offs
- Assisted forearm spring creates a distinct mechanical feel — not the smooth pump cycle of a Winchester SXP or Mossberg 590
- No optic mounting provisions — limited to bead sight only without aftermarket gunsmithing
- Synthetic stock lacks texturing — can feel slick with wet hands or gloves
Video review
Expert review
Specs at a glance
About this product
What is the TriStar Cobra III Marine Pump 12 Gauge 18.5″ 5+1?
The TriStar Cobra III Marine is a 12-gauge pump-action shotgun designed as a corrosion-resistant general-purpose/defensive tool for environments where saltwater exposure is a legitimate concern. It utilizes a chrome-lined bore, Beretta Mobil chokes, and a unique spring-assisted forearm assembly. At 36.5 inches long and 6.2 pounds, it's a durable, no-frills platform. For those prioritizing rust resistance and adaptability, it's a notable option.
What is the TriStar Cobra III Marine pump shotgun used for?
The TriStar Cobra III Marine is used for general-purpose utility and defensive applications in damp, humid, or maritime environments. Its chrome-lined bore and matte silver finish resist corrosion significantly better than standard blued steel, while the 3-inch chamber handles everything from light #8 target loads to heavy 00 buck. The included Cylinder choke is optimized for close-range patterning, making it suitable for home defense or as a truck/boating shotgun where exposure to moisture is unavoidable.
How does the TriStar Cobra III Marine compare to a Stevens 555 Sporting O/U?
The TriStar Cobra III Marine is better suited for rough, corrosive, or defensive use, while the Stevens 555 Sporting O/U is superior for dedicated field or target shooting. The Marine's $349.99 price and pump-action design prioritize reliability and corrosion resistance over the Stevens 555's sporting ergonomics, precise balance, and break-action smoothness. For the shooter who needs a shotgun to live in a marine case or vehicle, the Marine's materials and assisted-pump system are more practical despite being 0.8 lbs heavier than an equivalent Stevens O/U.
What does it weigh and what are the dimensions?
The shotgun weighs 6.2 pounds (2.81 kg) with an overall length of 36.5 inches (927 mm). The 18.5-inch (470 mm) chrome-lined barrel contributes to these compact, maneuverable dimensions. The weight distribution is slightly forward-heavy due to the steel receiver and barrel, but the synthetic stock keeps overall mass manageable.
Who is this NOT for?
This shotgun is not for the competition shooter or traditional upland hunter wanting a fast-handling field gun. The assisted forearm spring adds a distinct mechanical feel to the pump cycle that purists may find non-traditional. It's also not ideal for those in arid climates who would be better served by a standard finish pump like a Mossberg 500 – you're paying for corrosion resistance you may not need. For those primarily shooting clays or hunting over dogs, consider the Stevens 555 series instead.
What's in the box?
You receive the shotgun, one Beretta/Benelli Mobil Cylinder choke tube, the standard forearm spring, and minimal documentation. A hard case is not included; plan for an aftermarket purchase. The spring-assisted forearm can be removed in under 2 minutes with a punch, allowing you to run it as a standard pump action.
Is the TriStar Cobra III Marine worth it at $349.99?
At $349.99, it's worth it specifically if you operate in a saltwater or high-humidity environment. The chrome-lined bore and matte finish provide a measurable durability advantage over similarly priced pumps without these features. If you need a basic, reliable pump for general use without corrosive concerns, a standard Mossberg Maverick 88 at around $250 may be the better value. This is a tool for a specific, punishing environment.
Key attributes
| upc | 713780231648 |
| manufacturer | TriStar Arms |
| manufacturer part number | 23164 |
| action | Pump Action |
| atf type | Shotgun |
| barrel length | 18.5" |
| caliber/gauge | 12 Gauge |
| capacity | 5 + 1 |
| chokes included | Cylinder |
| color | Silver |
| length | 37.25 |
| model | Cobra III Marine |
| package height | 3.25 |
| package width | 7.5 |
| product type | Shotgun |
| safety | Thumb |
| shipping weight | 7.775 |
| sights | Blade Front |
Frequently asked questions
- Is it compatible with Remington or Mossberg choke tubes?
- No, it uses the Beretta/Benelli Mobil choke system exclusively. The included Cylinder choke is threaded for this pattern; you must purchase aftermarket Mobil-compatible tubes from brands like Carlson's or Trulock for different constrictions.
- Does it fit standard 12-gauge sling swivels?
- Yes, the synthetic stock is pre-drilled for a standard 1-inch quick-detachable swivel cup at the rear. The magazine tube cap accepts a standard front swivel stud, allowing sling attachment in under 5 minutes with basic tools.
- How long does shipping take for an online-only firearm?
- Shipping to your selected FFL typically takes 3-7 business days after order processing. All firearms require shipment to a licensed dealer for the mandatory 4473 background check transfer, which adds 1-2 days for dealer processing.
- Can I return it if it doesn't cycle my preferred shell?
- Returns on firearms are strictly limited to manufacturer defects verified by TriStar's warranty service. For function issues, we recommend a 50-round break-in period with standard 2 3/4-inch, 1 1/8-oz target loads before evaluating reliability with defensive or specialty ammunition.
- Does this work with a magazine tube extension?
- No, the 5+1 capacity is fixed. The magazine tube is integral to the receiver design and not designed for aftermarket extensions. Increasing capacity would require permanent modification not recommended by the manufacturer.