Compared: Mossberg 500 Mariner and Remington 870 Marine Magnum 12 Gauge Shotguns

By the Guns and Shooting Online Staff

Probably the two most commonly encountered marine shotguns are the Mossberg 500 Mariner and Remington 870 Marine Magnum. The purpose of this article is not to tell you which gun is better, since we have concluded that they are functionally about equal, but to point out the similarities and differences. While generally similar in concept, there are detail differences between the two designs, which we will address individually.

The Remington 870 Marine comes with an 18" barrel and an extended six round magazine (7-shot total capacity). The Mossberg 500 Mariner is available with an 18.5" barrel and a standard five round magazine (6-shot total capacity), or a 20" barrel and an extended seven round magazine (8-shot total capacity). Guns and Shooting Online staff members own Mossbergs with both barrel lengths and the guns are otherwise identical, but for this article we will focus on the version with the five shot magazine and the shorter barrel.

Incidentally, although the Mossberg's advertised barrel length is 18.5", our Mariner's barrel actually measures 18.0", the same length as the Marine Magnum's barrel. Our Mariner's measured overall length is 38.25", while the Remington Marine Magnum's measured overall length is 38.75". The length of pull measured 14" for both guns. These actual measurements are somewhat different from the numbers supplied by the manufacturers. Here are the catalog specifications for both guns.

Mossberg 500 6-Shot Mariner Specifications

Mossberg 500 6-Shot Mariner Shotgun
Mossberg 500 6-Shot Mariner. Illustration courtesy of O.F. Mossberg & Sons.
  • Type: Pump action repeating shotgun
  • Item number: 50273
  • Gauge: 12
  • Chamber: 3"
  • Barrel length: 18.5"
  • Capacity: 5+1
  • Choke: Cylinder bore
  • Metal finish: Anodized aluminum receiver, Marinecote barrel
  • Stock: Black synthetic w/black recoil pad
  • Sight: Brass front bead
  • Overall length: 39.5"
  • Length of pull: 13.875"
  • Weight: 6.75 pounds (empty)
  • Included accessories: Pistol Grip Kit, sling swivel studs
  • 2012 MSRP: $593.00

Remington 870 Marine Magnum Specifications

Remington Model 870 SPS Marine Magnum Shotgun
Remington 870 Marine Magnum. Illustration courtesy of Remington Arms Co.
  • Type: Pump action repeating shotgun
  • Order number: 25012
  • Gauge: 12
  • Chamber: 3"
  • Barrel length: 18"
  • Capacity: 6+1
  • Choke: Cylinder bore
  • Metal finish: Electroless nickel plated barrel and receiver
  • Stock: Black synthetic w/black recoil pad
  • Sight: Silver front bead
  • Overall length: 38.5"
  • Length of pull: 14"
  • Weight: 7.5 pounds (empty)
  • Included accessories: Sling swivel attachments, black nylon sling w/swivels
  • 2012 MSRP: $829


Both are 12 gauge pump guns with streamlined receivers, short barrels, 3" chambers, hollow black synthetic stocks with visible mold lines and specially coated metal parts to resist saltwater corrosion. The pump handles are grooved for a secure grip. The trigger guard assemblies are black plastic, similar to the stock material. Both guns balance right at the front edge of the receiver, for a slightly muzzle heavy feel when empty that is accentuated when the magazine is full. These Marine shotguns are equally useful for terrestrial defensive shotgun applications, being the same (except for color) as tactical black versions of the Model 500 and Model 870, only more rustproof.

Mossberg calls their patented metal protection Marinecote and they don't reveal exactly what it is, but it works. Remington's process is stated to be electroless nickel plating, which also works. The guns are protected inside and out and have a good reputation among long time users. These metal finishes are matte silver in color, which contrasts with the black plastic stocks and is more attractive than the usual matte black tactical shotgun finish. The dull silver barrels are also easier for the shooter to align at night. Sighting is by means of a shallow groove in the top of the receiver and a metal bead front sight.

The slide handle connects to the action with dual action bars in both guns. Most internal parts are formed from sheet metal stampings. The trigger group can be removed from either gun by punching out one (Mossberg) or two (Remington) large pins that are designed for easy removal. Shells are loaded from the bottom and eject from the right side of the receiver. The magazines can be topped-up with the chamber loaded and without taking the gun out of action.

Both guns shoot to the point of aim if the stock fits the shooyer. The barrels are straight cylinder bore, which seems to be the norm for tactical shotguns. Even so, you must aim carefully at a specific target, as you would with a rifle, if you expect to score hits. At normal shotgun ranges, even with buckshot, there is not enough spread from a single round to hit more than one human size target, despite what you may have seen in the movies. Nor will the impact blow a bad guy off his feet and through the nearest window, we are sorry to say.

Both guns are chambered for 3" Magnum shells. However, we recommend shooting standard velocity (not magnum) 2-3/4" shells to help keep recoil at tolerable levels. The 7.5 pound Remington gun is simply not heavy enough to temper the recoil of 12 gauge Magnum shells and the lighter 6.75 pound Mossberg is even worse in this regard. 12 gauge, 2-3/4" and 3" magnums kick very hard and this slows recovery time for subsequent shots. Tactical shotguns need to be controllable and standard 12 gauge loads pack plenty of stopping power.

Buckshot is the most common defensive shotgun load, although bird shot is sufficient at typical indoor ranges and Foster type rifled slugs can be used in the cylinder bore barrel if you need more penetration or longer range, for example to punch through the fiberglass hull of an aggressor vessel. G&S Online owner Chuck Hawks kept a bandoleer with all three types of ammunition available aboard his small cabin cruiser.

Because both guns are so popular, plenty of after market accessories are available. These range from tactical flashlights and lasers that attach to the front of the magazine tubes to replacement buttstocks and pretty much everything in-between.


Mossberg provides shotguns to the U.S. military. They claim that only their Model 500/590 tactical shotguns fully meet or exceed the U.S. military MilSpec 3443 requirements for endurance, chemical resistance, drop tests, patterning, parts interchangeability and quality assurance. Advertised features include an anti-jam shell elevator and dual extractors for reliable operation. The Remington 870 uses a single extractor and a more conventional shell elevator. Neither shotgun, however, jammed in our testing or has ever had a problem functioning.

The Mossberg's shell elevator remains up, tight against the bottom of the bolt, when the gun is cocked and ready to shoot. It only drops down to elevate a cartridge as the action is pumped and immediately returns to its "up" position at rest. The Remington's shell elevator is down at rest. It only moves up to elevate a shell to the chamber when the action is operated and immediately drops back down. There is not a big difference, but we feel the Mossberg is easier to load, because its shell elevator is out of the way.

The 870's receiver is machined from a block of steel. The 500's receiver is aluminum alloy. Since the bolts of both guns lock into a barrel extension, receiver strength is not an issue. The aluminum receiver is makes the Mossberg gun lighter, but we like the solid feel of the Remington and the extra weight helps reduce recoil.

The top of the Mossberg's receiver has longitudinal grooves to break up reflected light; the Remington's receiver does not. We like the grooves.

Operating (pumping) the actions of these guns feels different. The Marine Magnum's pump action has less initial resistance, but a little more resistance throughout the stroke. The Mariner has more resistance at the start and for the first half of the stroke, but when that resistance is overcome, the handle comes back more easily the rest of the way. We slightly prefer the feel of the Remington Marine Magnum's action, but could detect no difference between the two in operating speed.

The 870's trigger pull measured a smooth 3.75 pounds per our RCBS pull gauge. The 500's trigger pull was much heavier, at 7.75 pounds. The Mossberg trigger is wider and smooth with more curve; it feels better against the finger, but the heavy pull makes it clearly inferior. The trigger pull is one of the most obvious operational differences between the two guns.

The Mossberg 500 safety is a plastic slider located on the top rear of the receiver, which we regard as a more convenient location than the Remington 870's crossbolt safety, located in the rear of the trigger guard. On the other hand, the Remington crossbolt is made of steel, not plastic.

The Remington's release to unlock a closed, unfired action for opening is at the front left of the trigger guard. The Mossberg's action release is at the left rear of the trigger guard. Both work fine, but we found the Remington's location easier for our finger to find. The Mossberg release requires less force to depress, though.

A shotgun stock positions the eye over the receiver and barrel and essentially serves as the rear sighting system. What we can say in that regard is the Mossberg stock has a bit more drop and considerably less pitch than the Remington stock. Your physiology will determine which stock fits better and shoots most naturally to your point of aim.

The Remington stock's grip is considerably smaller in diameter than the Mossberg's thick grip. The Remington's comb is slightly fluted, the Mossberg's is not. Consequently, the Remington stock feels much better at the wrist.

Both stocks terminate in black recoil pads. However, the Remington SuperCell pad has more give and does a better job of softening recoil. It also has a smoother finish that is less likely to catch on clothing.

Mossberg supplies stainless steel quick detachable sling swivel studs front and rear on the Mariner. The Remington Marine Magnum comes with a steel sling swivel stud in front, but only a chintzy little loop molded into the plastic stock for the rear sling swivel attachment point.

The Mossberg comes with a Pistol Grip Kit that allows replacing the shoulder stock with a pistol grip. This makes the gun harder to shoot accurately, but shortens its overall length considerably and allows it to be stowed in restricted spaces that might not be long enough for the gun with the regular buttstock attached. In small boats with cramped interiors, the pistol grip can be a useful accessory.

The Remington Marine Magnum is supplied with a rather nice black nylon sling and detachable sling swivels. A sling can be a useful accessory on a marine shotgun. You have to provide your own sling and swivels for the Mossberg Mariner.

The 6-Shot Mariner's barrel is secured by a threaded cap at the front of the magazine, just like Mossberg 500 field guns. The advantage of the standard length (five shot) magazine is that it allows the gun to accept regular Mossberg 500 interchangeable barrels. For example, we ordered an extra 28" vent rib barrel, so we could also use our Mariner for hunting just by changing barrels. This makes the 6-shot Mariner much more versatile than the extended magazine 8-shot Mariner or the Remington Marine Magnum, which also has an extended magazine.

Perhaps the most obvious difference between these two guns is the MSRP, with the Mossberg Mariner being $236 less expensive than the Remington Marine Magnum in 2012 dollars. That will buy quite a few boxes of shotgun shells. On the other hand, if the Remington gun fits you better and is easier for you to use, your life is probably worth an extra $236 of insurance. Cost is important to all of us, but we would not let it be the sole determining factor when choosing a defensive weapon.


Mossberg owners generally give high marks to the Model 500 Mariner and Remington owners seem equally satisfied with their Model 870 Marine Magnums. Both groups seem happy with their choice in marine shotguns. Most owners use their guns for home, as well as boat, defense.

Among the four of us on the Guns and Shooting Online staff who are also boaters, both brands are represented. We use our marine shotguns for home, as well as boat, defense and we are all satisfied owners. We therefore seem to be right in the mainstream. Our conclusion is that you cannot go too far wrong with either of these marine shotguns.

We have pointed out the similarities and differences between the two guns in this comparison. Let personal preference be your guide.

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