Slickguns Review: Mossberg 590M Pump Action Shotgun
I have long been a fan of Mossberg shotguns. The affair started with one I carried during Operation Iraqi Freedom back in 2003. It saved my life many times.
Despite that hard-earned loyalty, I was one of those who put the shotgun in a rack when I could pick up an AK. It wasn’t because I felt outgunned, as many critics suggest. Most of our engagements were well within the shotgun’s lethal range. Rather, my decision came down to reloading. Reloading the shotgun took more time than I was willing to spare.
I’m not telling you that a pump-action shotgun is the best choice for combat. However, for thousands of police officers and armed citizens, the shotgun is the preferred choice. (In some areas, it may be the only choice.) If those folks are involved in a lethal encounter with said shotgun, the speed-reload problem will be no different than it was in Iraq.
We all know changing a magazine is much faster than trying to download and upload different munitions, too. My select-slug transition. i.e., from buckshot to slug, is pretty fast with my duty shotgun, but I’d rather just lock a fresh magazine of 10 slugs in place and go about my business. With the news of the Mossberg 590M Mag-Fed, this is now reality.
The 590M is a magazine-fed variant of the company’s 590 military-grade pump shotgun. It maintains all of that model’s toughness and reliability, but adds the ability to change mags with capacities of five, 10, 15 or 20 rounds. The double-stack magazines are sturdy and feature heat-treated steel feed lips. The bodies are wide, but not overly cumbersome, and they utilize a three-piece design that allows the floorplate to be removed for maintenance. Inside, there is an anti-tilt follower and ASTM-A-228 (piano wire) spring that has been purposefully engineered to provide years of service.
Loading the magazines is not an arduous task. I found that only the last two to three rounds needed a little extra effort when nearing full capacity. As you might imagine, a magazine with 10 to 20 rounds of 2¾-inch buckshot can get fairly substantial, so Mossberg engineers designed a very robust yet clever magazine locking system.
Addition by Subtraction
First, designers ditched the magazine well for a wider loading port on the bottom of the shotgun, and the shell lifter was removed. The front of the magazine is placed in the loading port and an angled wedge on the front of the magazine interfaces with an insert where the opening of the magazine tube used to be. Once the front of the magazine is in the port, the user then rotates the rear of the magazine up until the ambidextrous magazine catch locks it firmly into place. This might sound complicated, but inserting the magazine into the 590M was intuitive. Everyone that I have had try it mastered the movement within minutes.
There are three notches milled on each side of the bottom edge of the receiver. These notches engage lugs at the top edge of the magazine. These six lugs not only make for an extremely tight lock up by increasing the surface area for contact, they allow the magazine to engage deeper into the receiver, which minimizes the angle a shell needs to move from the magazine to the chamber.
The magazine catch and magazine release button are likewise genius. The ambidextrous magazine release button located just in front of the triggerguard allows our trigger finger to release the magazine. (This is the same familiar method used to drop a magazine on the AR-15 platform.) When pressed from either direction, the button rotates slightly in a helical pattern, disengaging the catch from its engagement at the rear of the magazine. All styles of the magazine fell freely from the receiver during testing.
If there is any downside to the magazine system, it’s that it is limited to using 2¾-inch shells. For tactical or defensive use, this isn’t a big deal, but I’m sure there are some shooters (or hunters) that would like to shoot from their existing cases of 3-inch shells.
The rest of the 590M is predictable. The tang-mounted safety button is like that on the 500 and 590 shotguns. The ambidextrous magazine release and the slide release lever that’s located behind the triggerguard make this an ambidextrous shotgun. There are no odd hand movements necessary to manipulate the 590M safely and efficiently. It’s all right there and easy to use without having to break our firing grip.
For those reading this Slickguns Review who are in charge of buying shotguns for an agency, the 590M should be a consideration. Between 10 and 20 percent of all police officers are left-handed. Teaching right-handed instructors how to teach the left-handed shooter how to adapt is always a challenge.
Being magazine fed, the 590M also streamlines the download and unloading procedures. If the shotgun has a round chambered, simply ensure the shotgun is on safe, remove and secure the magazine, then cycle the action to eject the round from the chamber. The round can be caught or retrieved and then reloaded in the magazine. There is no worrying about trying to eject a round from the chamber without disturbing the rounds already in the magazine tube.
The Mossberg action remains the same. Inside are twin action bars and dual extractors. Interestingly, the bolt had to be modified to help it push the round up and out of the magazine and into the chamber. You have to look closely to notice the difference, but the 590M definitely has a new bolt.
There are two versions of the 590M available, one with ghost-ring sights, a heat shield, a tri-rail forend and removable chokes. Then there’s the basic model, which is represented by G&A’s test gun. It has a clean, cylinder-bore barrel and a bead sight. The top of the receiver is drilled and tapped for an optic mount or a length of Picatinny rail. I imagine that most owners, including myself, will add the rail for an optic. I’ve done plenty of good work with a bead up front, but this shotgun begs for a small red dot sight.
Both versions come with Mossberg’s tried-and-true synthetic buttstock with rubber recoil pad, which gives shooters a 13.8-inch length of pull. Both versions are also finished in matte blue and both come with Mossberg’s famous heavy walled barrel.
I was fortunate to receive a 590M several months before the official release, so I’ve had the opportunity to put just less than 1,300 rounds of mixed bird, buck and slug through it. I’ve been extremely happy with the performance thus far.
I found the shotgun balances best with a 10-round magazine inserted, but because the magazine hangs under the middle of the shotgun, even the big 20-round mag does not make the 590M feel unbalanced. The length of the 10-round mag is optimal when shooting in low positions, but I found myself often defaulting to shooting with the provided 10-round mag when shooting drills or trying to push myself to shoot faster on steel.
Initially, the 590M action was stiff, but after a couple of hundred rounds, it smoothed out nicely. Shooting this shotgun was easy, with a very nice trigger for a stock shotgun. Ours measured 61/2 pounds. Accuracy was good for a bead-sight shotgun, especially since my go-to defense load — Federal’s LE 132 00 (nine-pellet 00 buckshot with flight control) — loves cylinder bores. As the distances grew, I noticed that the shotgun shot slightly to the left. This is not uncommon with bead-sighted shotguns, but since I plan on putting a dot on it after the Slickguns Review, it’s a moot point for me.
Manipulations were also easy and familiar. After a little time running the gun, I found that the best way to reload the 590M was to tuck the buttstock under my primary arm and dip the muzzle slightly toward the ground while rotating it slightly inboard. This ensured that the magazine dropped free and provided the fastest angle to insert the new magazine.
I haven’t had a malfunction with the 590M, but a loose round would follow the magazine out of the loading port on occasion as I removed a full 15-round magazine after chambering a round. While not technically a malfunction of the gun, it was an observation that needed to be shared for you to be aware of.
While the 590M is not the solution for everyone, if I were limited to using one shotgun for personal defense, I would select this one. It’s not perfection, but nothing really is. There’s always a compromise between weight and capability, but I believe the Mossberg has really found a sweet spot with this one. It’s that good.
Editor’s Note: The author wishes to inform the reader that he had been paid to host several promotional videos for Mossberg prior to this evaluation, which can be viewed online at mossberg.com. This work did not influence the objectivity of this Slickguns Review.
Type: Pump action
Chambering: 12 ga. (2¾ in)
Capacity: 10 rds. (5-, 15- and 20-rd.
magazines are available)
Barrel: 18.5 in.
Choke: Cylinder (fifixed)
Overall Length: 39.5 in.
Weight: 7 lbs., 12 oz.
Finish: Matte blue (steel)
Stock: Synthetic, black
Sights: Bead (front)
Trigger: 6 lbs., 8 oz. (tested)
Manufacturer: O.F. Mossberg and Sons,
Photos by Alfredo Rico
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