Mossberg’s Mag-Fed 590M is Reinventing the Pump Shotgun

I’m a dedicated student of the defensive shotgun. While I can’t shoot skeet worth a damn, I’m solid with a short-barreled scattergun. When Mossberg and Remington jumped into a box-fed arms race, I was optimistic. Now that I’ve spent some time behind Mossberg’s 590M, I’m hooked.

The Mossberg 590M with a 20 round magazine.

Why is the mag-fed shotgun needed? The Mossberg 590, and the Remington 870 are both formidable beasts. Even with their shortest factory configurations, I find both a bit long for indoor use. When you shorten the barrels, though, you inevitably cut into capacity.

Some of the bullpup designs aimed to solve this dilemma. The Kel-Tec KSG is compact, but the balance is odd and it has a steep learning curve (and a wide forend). Auto loaders are an option, but they tend to be picky eaters.

The mags come in 5, 10, 15, and 20 round configurations. (The 5 isn’t pictured).

Mag-fed pump shotguns combine increased capacity with almost a design that’s been in use longer than any of us have been alive. It is a logical combination finally made practical by material science. And both Mossberg and Remington are making “firearm” versions with bird’s-head grips that are also very compact.

The gun below is a full-sized 590M. The 590 is an over-built 500, and the increased magazine capacity will allow for it to hold up to 20 rounds.

The new magazine well of the modified Mossberg classic.

The frame and the internals have been modified to accommodate the magazine’s unique feed mechanism. This means you can’t simply take an existing 500 or 590 and convert it to take the new Mossberg magazines.

Adaptive Tactical, the company that created the Mossberg platform, has conversion kits available for those who want to do it themselves.

The cut-outs fit exactly, so long as you rock the mag in.

The magazines themselves are impressive. They’re heavy-duty. The polymer is thick, and built with ridges to add even more strength. The feed lips are made from hardened steel. The magazines are fat, wide, and rock in somewhat like an AK mag.

The ribs on the side of the mag provide strength and excellent texture.

They’re also really fun to run dry. There’s something novel about doing a mag-dump from a 12 gauge. It is oddly exhausting, and a great test of skill and stamina. With decent buckshot, the force of 20 rounds will stand you up straight.

Loading the magazines is easy enough, and changing mags is as intuitive and simple as it is with most magazines. That’s the point. What is slightly more complex is how and where you might carry a spare magazine or two.

The rear of the mag has integrated steel feed lips.

From a tactical perspective, though, the availability of magazines allows for options. Keep slugs in one, and buckshot in another. These mags could easily be marked to differentiate between any number of available 12 gauge loads.

The front of the magazine is built of polymer only.

Very few of us take the time to disassemble and clean our mags, and some of them (like those for the Ruger 10/22) can be cumbersome, at best. These, though, are not. The simplicity of their construction can be seen from the outside.

The whole thing is held together with several screws. The metal clip is tempered so that it holds on the mag body with simple spring tension. Inside, the spring and follower is very easy to compress and keep in place while the body is reassembled.

The screws make disassembly and cleaning easy.

For those who are sticklers for balance, I can see the appeal of the 5 round mags. They’re small, though, and I can’t envision a situation that would require 5 rounds that wouldn’t be better with at least 10. This isn’t a really hunting shotgun, though I expect to see more of those with mags soon.

The 15 round 590M mag is the first one that I tend to really notice. It hangs almost below the midpoint of the gun, which makes keeps the weight in an optimal place, but the length can alter the feel of what would otherwise feel just like any pump shotgun.

The 20 round mag is easily the most fun. That’s a tremendous advantage over the classic Mossberg design.

10-15-20 round mags.

One thing that some have found daunting about these new mags is their price. The 20 round mag is over $100, but it is likely to be a one-time expense. While I’ve retired some AR mags, and many 1911 mags, these are less likely to be a consumable than most mags.

Are they worth it? Absolutely. I’ve owned many Mossbergs. My first was a Maverick. I’ve had several 500s, and still have a 590 that has a secure spot in the safe. This is the first shotgun that could kick it to the proverbial curb. If you haven’t held one with a 20 round mag, you should. It is an experience.

David Higginbotham is a writer and editor who specializes in everyday carry. David is a former backcountry guide in the Sangre de Cristo Mountains and Boundary Waters Canoe Area who was a college professor for 20 years. He ultimately left behind the academy for a more practical profession in the firearms industry and was (among other editorial positions) the Managing Editor for a nascent Mag Life blog. In that Higginbotham helped establish The Maglife's tone and secure its early success. Though he went on to an even more practical firearms industry profession still, he continues to contribute articles and op-eds as time and life allow.

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