Warfighter Wor­thy



The box mag­a­zine-fed 590M com­bines light­ning-fast reloads with Mossberg re­li­a­bil­ity


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.


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.


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.


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?


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.


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


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.


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.

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