FOR LIGHTNING-FAST 20-ROUND RELOADS & RIDICULOUS RELIABILITY, THE MOSSBERG 590M IS A TOP CHOICE
The box magazine-fed 590M combines lightning-fast reloads with Mossberg reliability
“THE 590M’S CLAIM TO FAME IS ITS ROBUST STANDARD 10-ROUND DOUBLESTACK BOX MAGAZINE.”
When it comes to competition, tactical or home-defense purposes, reliability is king, and ammunition capacity is a close second. Unless the rules of the competition or regulations prohibit, the more rounds on tap, the better. After that comes the ability to make a rapid reload.
Many types of rifles and pistols have had high-capacity magazines for years; shotguns have not. Most domestic shotguns, whether semi-auto or pump-action, are limited to how many rounds can be fit into their tubular magazines, usually four to nine.
If an extended magazine tube is installed, the capacity can be increased by anywhere from one to eight rounds if you can tolerate the magazine tube extending beyond the end of the barrel. The problem then becomes how to quickly reload that tubular magazine. With a lot of practice this can be done quickly by loading two at a time with up to four in-hand. Unfortunately, few of us will ever truly master this process. Most of us will find slapping in a new magazine much quicker.
Some manufacturers, especially foreign ones, make box-fed shotguns with single-stack or drum magazines, but they haven’t become mainstream and many suffer from reliability problems.
Enter the Mossberg 590M and Remington 870DM box-fed shotguns in 2018. The two share some similarities, but with its double-stack magazine the Mossberg definitely comes out on top in the capacity category.
JUST WHAT IS IT?
The Mossberg 590M is a box-magazine fed, pump-action 12-gauge shotgun based upon the 500/590 family of shotguns. These shotguns use a twin bar-slide action and are well-known for their reliability. The 590M’s claim to fame is its robust standard 10-round double-stack box magazine. Five-, 15- and 20-round doublestack magazines are also available. With this firepower available, score one for the 590M.
The heat shield model evaluated here (#50206) has replaced the Tri-rail version that was introduced at the 2018 SHOT Show. On the current model the heat shield is mounted differently, and the forend does not have molded-in 1913 Mil-std rail sections.
DESIGN AND OPERATION
Many of the components used in the
590M are similar to those used on the traditional 500/590 shotguns, but few are interchangeable. Gone is the elevator assembly. The magazine tube, now designated the “guide tube,” is blanked off at the receiver by the forward box magazine lug recess and only serves as a guide for the action slide assembly.
To accommodate feeding from the box magazine, modifications have also been made to the bolt and bolt slide. The bolt, however, still uses the rugged dual extractors found on previous models. The ejector also is still easily replaceable if it should fail.
The trigger assembly is different from that found on the 590 model, and barrels are not interchangeable between models.
Obviously, the aluminum receiver has been modified to accept the box magazine. Most notably, three slots have been milled into each side of the bottom of the receiver to accept the three lugs that are molded into each side of the top of the magazine. These serve to align and anchor the magazine into
exactly the same position every time a magazine is inserted into the receiver.
In a major departure from other box-fed shotguns, the 590M does not have a magazine well. Typically, the magazine well serves to guide the magazine into a uniform position each time it is inserted. Unfortunately, at the same time, friction created by the interface of the magazine well and magazine slows down the loading process and often prevents the magazine from dropping freely from the firearm when the magazine release button or paddle is operated. Score another one for the 590M.
Magazines are inserted using by the same “rock and lock” method as the AK-47 platform. A forward lug on the magazine locks into a stationary recess in the receiver just behind the guide tube. The magazine is then rocked to the rear, where it locks into the magazine catch housing assembly. This bi-lateral magazine catch can be operated from either side by pushing a release button similar to that on an Ar-style rifle. Pushing either of these release buttons causes the magazine to drop free under its own weight. Just make sure that it doesn’t drop on your foot.
Operating controls on the 590M will be familiar to anyone who has used a 590 for any length of time. The trigger has the same feel, the two-position safety is in its usual location at the top rear of the receiver, and the action lock is placed behind and to the left of the trigger guard.
Sights are Mossberg’s standard fully adjustable tactical ghost ring rear and post front sight. The front sight has a fluorescent orange ramp. The receiver is also drilled and tapped to accept a Picatinny rail section or scope base for mounting an optic.
The fixed-length, black synthetic buttstock has a soft ¾-inch thick rubber buttpad to help mitigate recoil. By using a FLEX adapter, the 590M is compatible with the Mossberg FLEX buttstock system. FLEX forends, however, are not compatible with the 590M.
The heart of the 590M is its magazine, which is made for Mossberg by Adaptive Tactical. According to the patent number and United
States Patent Office records, the patent for the design of this magazine was filed on September 16, 2011, and granted on May 28, 2013. Where has it been for five years?
Magazines are constructed in two basic parts. The upper portion is common to all magazines and provides the transition from double stack to single stack, center feed. The lower portion varies in length according to the capacity of the magazine and is solidly attached to the upper portion using eight self-tapping countersunk screws. The footprint of the lower portion measures roughly 2 inches by 3 inches.
The internals of the magazines consist of hardened steel feed lips, over-molded steel shell ramps, anticant rounded follower, ASTM-A-228 music wire spring and an easily removable floor plate. These magazines are extremely robust and well-made but are relatively light, with the 10-round version weighing in at 20 ounces, empty.
“THEY ALL FED AND FUNCTIONED WITHOUT A PROBLEM. EVEN WHEN I MIXED TYPES AND BRANDS OF AMMUNITION, THE 590M DID NOT COMPLAIN.”
What really makes the magazines extraordinary is that shotgun shell dimensions vary significantly from brand to brand, and even lot to lot. Their dimensions are nowhere near as tight as those for metallic rifle and pistol cartridges. This presents a significant challenge to anyone designing a magazine such as the one used by Mossberg.
The optional magazines are a bit expensive at $101, $127 and $140 for five, 15 and 20 rounds respectively, but why buy the 590M if you’re not going to buy the 20-round magazine too?
Initially, only two models of the 590M were available. First is the basic version, item number 50205, which has a bead front sight and a fixed cylinder bore. The second model is item number 50206 and is the one evaluated here. As I was completing this article, Mossberg announced a Shockwave version. I’m sure that once production has started to meet demand for these models, others will follow.
I would be very surprised if Mossberg isn’t also working on a box-fed model 930. Why wouldn’t
they? How about a 930M JM Pro version?
FEEDING THE BEAST
For this evaluation, multiple brands and types of birdshot, buckshot and rifled slugs were used. For competition purposes, I used Federal 3 dram equivalent, 1 1/8 ounce, #7 1/2 shot. It functioned perfectly. For general testing I used the Federal loads that I use in competition, Independence 3 dram equivalent 1 1/8 ounce, #8 shot, and various 1 to 1 1/4 ounce, 2 3/4 to 3 1/4 dram equivalent, #6 to #9 shot shells from partial boxes. Again, all fed and functioned without a problem. For defensive evaluations I used 1-ounce rifled slugs from Winchester, Federal and Hornady, #4 buckshot from Federal Premium, and #00 buckshot from Federal Premium and Hornady. Once again, they all fed and functioned without a problem. Even when I mixed types and brands of ammunition, the 590M did not complain.
SIGHTS AND OPTICS
The fully adjustable ghost ring rear and post front sight work well, but for this evaluation (especially for competition purposes) I installed a Holosun model HS510C circle-dot reflex sight. This required the removal of the rear ghost ring sight assembly and the
“THE ABILITY TO MAKE LIGHTNINGFAST 20-ROUND RELOADS SIMPLY CAN’T BE OVERSTATED.”
installation a section of Picatinny rail on the drilled and tapped receiver. This was done in less than a half hour.
The Holosun HS510C reflex sight was an excellent addition to the Mossberg 590M. They only issue with this combination is that it requires the shooter to lift his/her cheek slightly off of the stock to look through the optic. An aftermarket buttstock or riser would easily remedy this inconvenience.
A QD mount is built into the HS510C for easy attachment to any Picatinny rail.
The reticle can be configured for a 2 MOA dot only, 65 MOA ring only, or the two combined. Ten daylight and two nightvision-compatible brightness settings are available. Adjustments are 0.5 MOA per click. The unit weighs only 7.6 ounces.
AT THE RANGE, IN COMPETITION
I fired the 590M on multiple occasions. The first range session was to sight-in the Holosun HS510C reflex sight, confirm that the shotgun functioned properly and to become familiar with its operation. The pattern was hitting where I wanted it at 20 yards within five shots. I then fired 20 more rounds of birdshot to make sure that the magazines functioned properly.
Next came a one-day tactical 3-gun match. The 590M was used on two of eight stages. The one thing that I couldn’t practice was to remember to rack the shotgun after the first shot. I had previously been using a semi-auto shotgun in these matches, so racking the shotgun after each shot had to be learned. On both stages I hesitated after the first shot before operating the slide. Subsequent shots were not a problem. The 590M did its part and helped me earn a ninth-place finish out of 36 competitors. When I approached the shotgun-only stage, I was confident that the 20-round magazine would easily get me through the 16-target course of fire. Someone must have told the person who set that stage up that I had a 20-round magazine, because they had added a
Texas Star to the course for a total of 22 targets (double-helix, Texas Star, 9 poppers and a stop plate). Not to worry, I just dropped the empty 20-round magazine and slapped in a full 10-rounder.
I made a final trip to the range for slug and buckshot accuracy/grouping evaluations. I took one shot at 25 yards using Winchester 1-ounce Foster slugs to find that the Holosun HS510C was dead-on. At 50 yards the
Hornady #86234 American Whitetail 1-ounce rifled slugs had the smallest average for three 3-shot groups at 1.8 inches. Two of those groups were right at 1.5 inches.
Buckshot hit at the point of aim at 20 yards. I used three types of 00 buckshot and one type of 4B buckshot. Both the Hornady Critical Defense 00 Buckshot and the Hornady American Gunner Reduced Recoil 00 Buckshot had group sizes that I expected at 20 yards. The Critical Defense 00 buck produced an 8 1 3/16-inch average for three separate shots and the American Gunner Reduced Recoil 00 buck returned an 11 1/6-inch average. What surprised me was how tight the pattern was for the Federal Premium Personal Defense 12 gauge 00 buckshot. The average for three separate shots was 4 3/16 inches with one group at just 1 7/8 inches.
The only issue, if you can call it that, that I found with the 590M was that with a full magazine the action was a bit stiff to operate. I blame that on the upward pressure exerted by the shell on the bolt slide. Initially I was concerned about the weight of the 20-round magazine and its effect on balance and swing. With the weight of the magazine in the center of the shotgun, it was not a problem. I didn’t even think about it during the match.
This one is definitely going to find a home in my gun safe. During all aspects of this evaluation, and specifically during competition, the Mossberg 590M functioned flawlessly. There really is nothing like a pumpaction shotgun for reliability.
I have reviewed several high-capacity semiautomatic shotguns over the past couple years. While they all ran well at times, they were picky about what ammunition they liked. Even when I found ammunition that seemed to work reliably and bought a couple of cases of it, at some point in time the semi-autos would decide that they didn’t like
it anymore and jam, usually in the middle of a match. When they worked, they were great; when they didn’t, jams were usually very difficult to clear.
The ability to make lightning-fast 20-round reloads simply can’t be overstated. No matter how good you are at speed loading your tube-fed autoloader, it isn’t even close to being as fast as dropping an empty magazine and locking in another.
While the attributes of the 590M are outstanding for competition and home defense, for the warfighter those attributes are even more important. When their lives may depend upon a few extra rounds from a fast reload during a firefight, the Mossberg 590M could make a real difference.
When it comes to high capacity and reliability in a 12-gauge shotgun, I don’t know of anything that can match, much less beat, the Mossberg 590M.
Four doublestack magazines are available for the 590M. From left to right they have 20-, 15-, 10- and 5-round capacities. These magazines are very rugged, yet reasonably light.
The heat shield on top of the barrel separates the operator from the hot barrel after 20 rounds of 12-gauge ammunition have been fired in rapid succession.
High-performance fluorescent orange paint is used on the drift adjustable ramp front sight.
A look into the open receiver from the bottom shows the guides for the bolt to follow. The underside of the receiver with the bolt closed shows the bolt slide and the area that strips the shell from the magazine.
The standard black synthetic buttstock with ¾-inch-thick rubber recoil pad is adequate, but with the installation of a FLEX adapter the full line of FLEX buttstocks can be fitted to the 590M. The trigger assembly is similar to that of the 500/590 shotgun line, and the action release lever is located behind and to the left of the trigger guard. The magazine release can be operated from either side by depressing either of the release buttons.
The Holosun HS510C fits nicely on the 590M using a blued Picatinny rail/scope mount attached to the drilled and tapped receiver.