After the debut of the Mossberg 590M at SHOT Show this year, both of America's favorite pump shotguns have firmly embraced the detachable magazine configuration, with the Remington 870 DM having come out a few weeks prior.

It’s obvious both gun-makers have been working on their respective detachable box mag shotguns for a good while—after all, each model is arguably the flagship shotgun for Remington and Mossberg. At the very least, the time-tested pump guns are both companies’ best known models, so big changes like this aren’t made lightly.

While they are similar in concept, the 870 DM and 590M are quite different in execution.

The Magazines

The 870 DM hit the market first, with one basic tactical model released and a full line promised in the beginning of 2018, all of which were on display at SHOT, though the guns were not on the firing line for Range Day.

The Mossberg 590M at Range Day with its various magazines.
The Mossberg 590M at Range Day with its various magazines.photo by Dave Maccar

First, let’s talk about the magazines, after all, that's why we're here. Pump shotguns have long been favored by law enforcement and the military, in specific roles, because of the variety of loads they can fire, their devastating impact, and their ability to perform unique tasks like door breeching, along with reliability and affordability that gas guns simply can't provide.

Their only drawback has been that, while reliable, pump guns are slow to reload, each shell having to be fed into the mag tube one at a time. There’s no getting around it. Sure, there are speedloaders for competition shooters, but they're hardly practical in a tactical situation.

While there have been a number of semi-auto mag-fed shotguns on the market for a while, their reliability usually ends up in the “finicky” range, with the magazines themselves often the biggest problem. Of course, with significant upgrades and customizing, these guns can run well, but they haven’t become the standard for competition or tactical applications for a reason, beyond cost.

Remington 870DM magazines (top) are priced for about $35 and come in 3- and 6-round capacities. Mossberg 590M magazines come in a variety of capacities and range in price from $101 to $140.
Remington 870 DM magazines (top) are priced for about $35 and come in 3- and 6-round capacities. Mossberg 590M magazines come in a variety of capacities and range in price from $101 to $140.mfg photo

Shotgun shells were simply not designed to be stacked on top of one another. For a full explanation of why it has been such a difficult engineering problem to overcome, check out Bryce Towsley's deep look at the issue here.

Basic Design

The Remington 870 DM magazine is a fairly simple single-stack design, which means the mags are no wider than a shotgun shell, but they get long pretty quick.

The mags are a proprietary design produced by Remington. They have a polymer body attached to a top portion, including the feed lips, made of steel with an orange, ramp-shaped follower. At the rear of the feed lips are two prongs that hold the rim and brass of each shell as it feeds.

A 6-round Remington 870 DM magazine.
A 6-round Remington 870 DM magazine.mfg photo

From our field test of the 870 DM, the magazines were reliable and reasonably easy to load once you get the hang of it. The shotgun didn't experience any failures or jams at the range, and ran pretty much like you'd expect an 870 to run.

The magazines are available in two capacities, 3-rounds (only included with the turkey-hunting model) and 6-rounds. And that’s it. And there has been no word on any extended mags or drum magazine options in the near future. So while a conventional 870 with an extended mag tube can get to an 8-round capacity, the 870 DM seems to be limited to 6+1 rounds, for now.

However, considering how much faster it is to slap in a new 6-round box mag, the short capacity is somewhat mitigated.

Mossberg's magazine is also a proprietary design, also with a polymer-lower and steel-upper design but with an emphasis on capacity. The 590M uses a double-stack magazine configuration, able to holder more shells in a shorter, but wider, magazine.

A close look at the feed lips and follower on the Mossberg magazine.
A close look at the feed lips and follower on the Mossberg magazine.mfg photo

While it makes the magazines a lot boxier and fatter, the smallest capacity, 5-rounds, is considerably shorter than the 870 DM’s 6-round mag. Plus, the Mossberg has three additional capacities available: 10-, 15-, and a whopping 20-rounds.

The idea of running 20-rounds without a pause and then having 20 more ready to go as fast as you slap in a magazines is…intriguing enough to get into reloading shells just to feed it.

And because all that ammo weight is more or less centered in the receiver, it remains balanced and not as awkward as you might think.

I ran a few mags through a 590M at Range Day, doing everything I could to get it to jam up, including working the slide ultra slow and intentionally short-stroking the action—nothing got the Mossberg to hiccup.

So, it seems both magazines are well designed. It remains to be seen how they will hold up to extended, heavy use in the elements, but for nimbleness and because it’s more streamlined, the 870 has the advantage of being less bulky and more streamlined. The 590M is bulkier and a little more unwieldy, but with a big advantage when it comes to capacity.

The Mossberg 590M takes 2.75" shells only, but the 870 DM can chamber 3" shells as well.
The Mossberg 590M takes 2.75" shells only, but the 870 DM can chamber 3" shells as well.file photo

Another fairly significant difference is price. You’ll be paying for that extra capacity, with the Mossberg magazines ranging from $101 to $140 each and currently, both models of the 590M come with one 10-round mag.

The 6-round Remington mags are comparatively cheap, with an MSRP of $34.95 each.

In this case, it seems the 870 DM would be a bit better suited to hunters who don’t need a high ammo capacity, but would benefit from a more compact gun and magazines along with the ability to run 3-inch shells—while the 590M (which is a tactical shotgun anyway) is better suited to law enforcement and the military (especially considering the price of extra mags), and home defense applications as well.

Remington 870 DM Mossberg 590M
Construction: Polymer lower, steel upper Polymer lower, steel upper
Configuration: Single stack Double stack
Capacity: 3- or 6-rounds 5-, 10-, 15-, or 20-rounds
Chambering: 12 gauge, 2.75” or 3” 12 gauge, 2.75” only
Price of Additional Mags: $34.95 each $101 to $140 each
Shotgun Price: $599 - $799 $721, $801

Magwells

Almost as important as the magazine itself is the way it interacts with the magwell.

Both magazines are bulky, wide, and fairly heavy just by the nature of what they hold, but I have to say, both systems, while being quite different, are smooth and robust.

The magwell on the 590M isn't really a magwell at all, as it's cut right into the bottom of the receiver where the elevator would be and doesn't extend below the bottom of the receiver. The retention system and release button is a small unit located between the front of the trigger guard and the back of the magwell.

The mags must be inserted at just the slightest cant with the front going in first and then rocking the rear of the mag into the locking mechanism. Even without a flare of any kind, it's easy for the mag to find its way, but holding the shotgun still in midair while trying to make sure a full 20-round mag is seated properly can be a little awkward.

To release, simple activate the ambidextrous mag-release button just in front of the trigger guard (roughly where the safety is on an 870) and tilt it out with your support hand. They do not fall free, but lock very securely.

The ambidextrous magazine release on the 590M is located just in front of the trigger guard.
The ambidextrous magazine release on the 590M is located just in front of the trigger guard.photo by Dave Maccar

The 870 DM works a bit differently with an AK-style magazine release lever located in front of the magazine well. It’s also, by nature, ambidextrous—activated by the index fingers of the support hand while pulling the mag free, though the normal push-button safety is not. Magazines on the 870 DM don’t fall free either.

The magwell on the 870 DM, instead of being more of a port cut into the bottom of the receiver, is actually a fairly traditionally shaped magazine well that is a separate piece, bolted to the receiver and curved slightly forward.

The lever-style release is a proven design for large, heavy magazines on rifles and also locks up perfectly securely—which is something I did get to try a few times on the SHOT Show floor. While it might take a little retraining for those used to an AR's controls and dropping mags with their index finger, it’s a smooth operation once you’ve done it a few times.

While it may seem that the magwells and releases are pretty much even, there is something I would like to see addressed on the 590M.

While Remington has released the 870 DM in six variants, including two with pistol grips (three if you count the TAC-14), Mossberg has only introduced the 590M in two very similar configurations, a standard 590 with a bead sight, and a more tactical version with ghost sights, a heat shield, and a tri-rail forend.

The 870 DM uses a magazine release lever located in front of the magwell and leaves its safety in the usual place.
The 870 DM uses a magazine release lever located in front of the magwell and leaves its safety in the usual place.mfg photo

However, both models feature a simple synthetic stock without a pistol grip.

Just as the slide release on a Mossberg 500 or 590 can be a little difficult to activate without moving your hand if a pistol grip is installed—I wonder if it will be difficult to reach the push-button mag release with the index finger of the shooting hand with that kind of grip.

Even if this is the case, it’s not a deal breaker, because the the ambidextrous button can be activated by the thumb of the support hand as it removes an empty magazine, though it would take some training and might be a little awkward.

Obviously, once someone gets a 590M and attaches a pistol grip stock, we’ll know for sure.

Overall MagWell Comparison

Mossberg 590M Remington 870 DM
Ambidextrous Release: Yes Yes
Solid Lock-Up Yes Yes
Ease of Operation: Very Very

Shotgun Packages As A Whole

The biggest and most obvious difference is that the 870 DM is already a full line of shotguns with a synthetic stock model, a tactical model with Magpul furniture, a hunting version with a thumbhole stock and optics rail, a classic model with hardwood furniture, and another tactical version with a breacher barrel, optics rail, and pistol grip stock.

The Mossberg 590M with a 10-round magazine in place.
The Mossberg 590M with a 10-round magazine in place.mfg photo

Additionally, Remington is also offering it’s wildly popular TAC-14 shorty shotgun in a DM configuration.

One thing you noticed when shooting the 590M is that the extra-long action bars pull the support hand a little farther out than normal, making it feel a bit awkward with the full-length stock. Being able to shorted the length of pull an inch or two would have made it more comfortable. The gun just feels big and it seems the receiver had to be lengthened a bit as well to accommodate the rather large magwell.

The 590M doesn’t seem like it can be cut down into a 590 Shockwave configuration without some tweaking, while the TAC-14 DM is already a thing, and with comparatively cheap magazines.

The 870 DM Predator, designed for hunting right out of the box and comes with a 3-round magazine.
The 870 DM Predator, designed for hunting right out of the box and comes with a 3-round magazine.mfg photo

While it’s almost certain the 590M line will soon expand, as it stands now, the 870 DM seems more adaptable, more streamlined, and to suited to a wider range of applications, albeit with a lower ammo capacity.

The 590M boasts a big on-board ammo advantage with a potential 20+1 round capacity, which will be the decision maker for some, depending on the intended application, though the hefty cost of additional mags has to be considered.

The Remington TAC-14 shorty non-NFA shotgun is available in the 870DM configuration, but there has been no such release for the Mossberg 590Shockwave...yet.
The Remington TAC-14 shorty non-NFA shotgun is available in the 870 DM configuration, but there has been no such release for the Mossberg 590Shockwave...yet.mfg photo

Specs Comparison

Gauge/Chamber Mag Capacity Barrel Length Barrel Type/Choke Sights Overall Length Weight Length of Pull MSRP
Remington 870 DM Base Model 12 - 2.75" 3 or 6 18.5" Cylinder Bore Bead 38.5 N/A 14" $599
Mossberg 590M 12 - 3" 5, 10, 15, 20 (comes with 10-round magazine) 18.5 Cylinder Bore Bead or Ghost Ring Sights 39.5" 7.75 lbs (unloaded) 13.87" $721, $801