The Remington 870 Special Purpose Marine Magnum is a 12-gauge pump shotgun built specifically for high-moisture environments. Both the barrel and receiver are finished with electroless nickel plating over the steel, which gives substantially better corrosion resistance than standard blued or parkerized finishes. The synthetic stock is matte black and the safety is a standard crossbolt design. 
 

Key Specifications: 

• Model: Remington 870 Special Purpose Marine Magnum 
• Gauge: 12 GA 
• Chamber: 3" 
• Action Type: Pump 
• Capacity: 6+1 rounds 
• Barrel Length: 18.5" 
• Overall Length: 38.5" 
• Weight: 7.50 lbs 
• Sights: Bead Front Sight 
• Stock Material: Synthetic (Matte Black Finish) 
• Receiver Material & Finish: Steel with Electroless Nickel-Plating 
• Safety Mechanism: Crossbolt 
   

Detailed Features: 

 
The electroless nickel plating is applied to metal components including the barrel and receiver. This is the primary distinguishing feature of the Marine Magnum versus standard 870 variants. Electroless nickel provides uniform coverage including inside bore areas, and holds up well to saltwater exposure, humidity, and rain better than blued steel. 
 
The 18.5-inch barrel keeps overall length to 38.5 inches, which is practical for storage and for maneuvering through doorways and tight spaces. Capacity is 6+1 rounds. The bead front sight is simple. The pump action on the 870 is one of the most field-proven designs in shotgun history, with parts and service widely available. 
 
The synthetic stock avoids the cracking and swelling issues that wood stocks can develop in wet environments. 
 

Usage Scenarios: 

 
The Marine Magnum's corrosion-resistant finish makes it the right choice for boat use, coastal duck hunting in saltwater marsh, or any environment where the gun will regularly encounter moisture. Home defense is a natural application given the short barrel and capacity. The 870 platform is well-suited for competitive shooting and range training given how widely parts and accessories are available.

Owners of the 870 Marine Magnum are buying it specifically for the electroless nickel finish, and that tends to be the most-praised feature in discussions. Users who keep guns on boats or hunt in saltwater environments report it holding up considerably better than standard blued shotguns in the same conditions.

The 870 pump action itself generates consistent positive comments about smoothness and reliability. Most owners have handled other 870 variants before and find the Marine Magnum meets the same standard.

The 18.5-inch barrel length is viewed favorably for maneuverability and home defense storage. Some users mention the gun's 7.5-lb weight as a downside for extended carry, though the trade-off is a solid, full-metal construction.

Occasional comments suggest upgrading the stock for better ergonomics or adding accessories like a sidesaddle or light mount, which is straightforward given the 870's accessory ecosystem.

The overall sentiment is positive, with most buyers treating it as a working tool rather than a range toy, and reporting it performs as expected in its intended environment.