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A Pump for Every Purpose: Mossberg Flex Review

by G&A Staff   |  March 22nd, 2012 23

Mossberg Flex

Last fall, Mossberg’s Vice President of Marketing, Tom Taylor, invited me down to South Carolina for a couple days to show me something he called “revolutionary.” I asked him for a hint, and he replied, “All I can tell you is it involves the Model 500.”

What, I thought, could possibly be revolutionary about the M500 shotgun? It just about defines the workhorse, white-bread, no-frills pump. I was silent for a moment, and Tom, sensing my hesitation, said, “Trust me. It’ll be worth your time.”

“OK.” I replied.

“You won’t regret it,” he said.

And I didn’t. What he had to show me was the new Flex system for the M500 (and M590 3-inch). The Flex permits you to instantly customize, configure and accessorize a shotgun with a wide variety of stocks, fore-ends, recoil pads and barrels using Mossberg’s unique Tool-less Locking  system. The TLS consists of a series of three connectors that allow a simple, tool-free method of switching stocks, fore-ends and recoil pads for any conceivable shotgun application. From a rugged tactical platform to a foul-weather hunting tool to a compact home defense gun, just one receiver does it all.

Flex system stock options include a tactical pistol grip and three all-purpose synthetic stocks in black or a choice of two camo patterns, each with a different fixed length of pull. Plus, there’s a six-position tactical stock and even a hunting/sporting stock with an adjustable comb. They all lock securely to any Flex system M500 (or M590) receiver via a rigid, metal-to-metal, quick-detachable TLS interface. And you can further adjust the length of pull by choosing one of three different snap-on/snap-off Flex system recoil pads in three different thicknesses. This allows for even more custom fit depending on the shooting applications, the amount of outerwear and the shooter’s stature. These attach to the stock via the second of the three new TLS latching systems. Flex system synthetic fore-ends range from tactical railed design to standard field and hunting shapes in black and various camo patterns so you can configure your gun to any purpose—on the fly, without tools—using the third TLS mounting mechanism.

The receiver itself is, of course, the proven M500 design, featuring nonbinding twin-action bars, positive steel-to-steel lockup and anti-jam elevator, anodized aluminum body and ambidextrous top-mounted safety. Moreover, any of Mossberg’s existing selection of M500 or M590 12-gauge barrels will fit any Flex system receiver and fore-end—short tactical barrels, vent-rib skeet barrels, camouflaged waterfowl barrels, tight-choked turkey barrels, cantilever-mount full-rifled slug barrels, whatever. The combinations are virtually limitless.

The TLS locking devices are engineered to withstand the hardest use, from combat to hunting.

Mossberg is starting out the Flex system with 11 new M500 and M590 Flex-receiver shotgun configurations ready to go. It has already got a total of 16 different aftermarket Flex stocks, fore-ends and recoil pads available for further Flexing any of the basic gun setups—plus all the M500 and M590 barrels available. Base model Flex shotguns currently include three M500 All-Purpose, four M500/M590 Tactical and four M500 Hunting options. Three of the M500 Flex All-Purpose and M500 Flex Hunting shotguns feature Mossberg’s Lightning Pump Action adjustable trigger system, which is user-adjustable from three to eight pounds with an Allen wrench to provide a creep-free pull. It’s the best damned factory-issue pump-action shotgun trigger on the market (says this 40-year veteran Illinois slug-gun deer hunter).

M500 Flex All-Purpose Models come with 26- or 28-inch vent rib, Accu-Choke-ported barrels with matte metal finishes or optional all-weather Marinecote finish, plus a full-length matte-black synthetic stock with medium recoil pad for a 141/2-inch LOP and a black matte standard synthetic fore-end. M500/M590 Flex tactical models are available with matte OD green and coyote tan finishes on barrels and receivers, and tactical tri-rail fore-ends that can accommodate a touchpad. Tactical stock options include either standard synthetic, six-position adjustable tactical stock or pistol grip. Barrel choices are either 181/2-inch Stand-Off barrel or 20-inch, both cylinder bore with six-round total capacity (nine rounds with the M590 Tactical). M500 Flex hunting models are available with 24-inch or 28-inch vent-rib barrels and choice of OD green, Coyote Tan, Mossy Oak Break-Up Infinity or Realtree Max-4 camo receiver finishes. Standard full-length stocks and fore-ends feature Infinity or Max-4 finishes as well.

Recommended retail prices currently begin at $593 for a black All Purpose M500 Flex with 28-inch vent-rib barrel and Accu-Choke and go up to $887 for an OD green tactical M500 Flex with 20-inch barrel, railed fore-end and XS ghost-ring sights.

No Flex in the Flex
When I arrived at the seminar and sat down to listen to the opening presentation, I confess that I was initially less than overwhelmed. There are lots of different stocks, fore-ends, recoil pads and barrels already out there in the marketplace for all major makes and models of shotguns. As for “quick change,” well, I’ve seen many such products that might have fit nicely at the outset, but they quickly became loose after a few on/offs. But as I began to pay closer attention to the details of the three-part Flex TLS mechanisms, I realized there was something different going on here.

The interchangeable recoil pads on the Flex buttstocks attach using two locking studs, which protrude from the pads and are clamped in place by a latching mechanism within the stock itself. The two-sided release panel in the stock is located at its toe and needs to be pressed upward from both sides at the same time to release the internal clamps from the recoil pad studs. The panel is sunken below the stock surface with a shield bar across its middle so that it’s virtually impossible for it to be inadvertently pressed and held down. But when you press it in and hold it, take a firm grasp and pull the recoil pad up and out, it pops right off. And it’s secure as hell. First thing I did when we took the guns out to the range for tryout was pound the butt end sideways as hard as I could against the concrete floor of the firing line before Tom Taylor’s horrified eyes in an effort to knock off the recoil pad. I didn’t succeed.

The fore-ends on the Flex system snap, unlock and lift off (and back on) angularly, with a firm press on a well-shielded pressure point—very much the same motion used to remove the forearm from an old-fashioned double. We worked the Flex fore-ends hard on the ranges, slamming them forward and back, and there wasn’t a hint of loosening.

Of course, the critical element in the Flex system is the interface between the receiver and the stock. That’s where the gun’s recoil energy really comes into focus, and that’s where any shotgun buttstock design is most likely to fail, even stocks meant to be permanently attached. Listening to Mossberg’s Vice President of Engineering, Bill Lutton, explain how the Flex system TLS stock connection worked I was, again, initially dubious.

No way, I thought, that the short aluminum stud coming out of the rear of the Flex receiver was ever going to hold up against 12-gauge recoil without loosening.

No way, I thought, that a release latch as easy to operate with just the thumb and forefinger as he was demonstrating could provide a truly solid lock.

Wrong again, Metcalf.

As Bill continued to explain the tight tolerances in the interface between stock and receiver and the way the slight angles in the lugs holding the receiver stud and the aluminum stud receptacle in the stock in alignment actually serve to tighten their connection rather than let it loosen, I began to appreciate the design. When I got my hands on the system to try it myself, I saw that he was right.

The fit is solid and tight. It’s easy to lift the release latch out of its slot and rotate it 90 degrees to release the lock, but when you go to pull the stock free from the receiver, you need to pull it back straight. The fit is so close that the slightest torque in the direction of pull will bind the closely fitted mating surfaces even more tightly and nothing will move. But it only takes a couple of tries to get the feel of it.

Will it stand up to years and years of countless switching back and forth of different Flex setups? Only tens of thousands of rounds will tell. But during two days of firing as a group, we probably did more on-and-offing between stock types and gun configurations and more pounding on clay targets and slamming down steel targets with different stocks switched back and forth than most individual users will do in a year or more. At the end, everything was still rock solid.

Considering its versatility and ease of custom accessorizing, you should probably think of the Flex as the AR-15 of shotguns.

See photos and specifications of the guns mentioned in this article and order from an inventory of thousands—all online through Gun Locator. Visit


  • Airstreemer

    I believe that this is the future of the gun industry. Why have a safe full of guns when you can have one gun that serves many purposes?
    Wouldn't it be nice if you could have a platform that would work as a rifle or a shotgun interchangeably?
    I love Mossberg! I have a 935 that I would not trade for anything!

    • BJC

      I am a Mossberg fan too I have a 500, 590, and had a 935, but this interchangeable platform is not new, Thompson has had it for many years. I have a contender and an encore, they are very fine guns, the only draw back is they are single shot. Don't know what took so long for other manufactures to come up with it. I think they will do good with it.

  • RoyJaruk

    "Considering its versatility and ease of custom accessorizing, you should probably think of the Flex as the AR-15 of shotguns."

    I think you've just insulted the entire Mossberg 500 line, Mr. Metcalf. You see, unlike the infamous Poodle Shooter, the Mossberg 500 ALWAYS works when you need it. I own a well used ex-police cruiser 500 with a 20 inch, rifle-sighted barrel, and it has never let me down.

    I understand what you were trying to say: that the new Mossberg Flex can be customized as every individual shooter wishes for the mission at hand, from home defense to deer hunting to turkey shooting and any other application for a shotgun you can think of; just as the AR-15 can be tricked out in an infinitude of ways to suit the perceived needs of its shooter. But when I think of the Stoner line, I don't think about the ways in which a shooter can customize his rifle. I think of the lack of reliabiity that has been getting our soldiers killed for going on 50 years now.

    You owe the Mossberg Flex an apology, I think. Or at least a clarification.

    • Kyle Meier

      The AR is'nt the platform it was many years ago. It's more reliable than nearly any rifle today. 'nam was a bad start but it wasnt the rifles design. some beaurocrat decided to switch the powder and get rid of the chrome linings. An average AR today can go 5000 rds with out a m/f. the .223 is a bit underpowered i agree but a switch takes seconds.

  • Toto C Potts

    Ok – I'm pretty much a Remington man but if a package containing all of the above (in the top picture) stocks (no need for redundant stocks), fore ends, and barrels to handle all my pump gun needs (turkey, deer, small game, clays, and house work) for around $1100-1200 street price I'd consider putting my 870 in the back of the safe. Considering I just spend $300 on a turkey barrel for my 870. Having 4 barrels, 2 stocks, 2 fore ends, and numerous recoil pads in one deal would make for an attractive deal and probably a bit of profit for Mossberg. Another approach might be to pick and choose the barrels, stocks and fore ends at the time of purchase – you'd pick either the 2 3/4" or the 3" receiver and select as many or as little "options" as you'd like – that may make for an interesting stocking arrangement between the dealer and distributor (forget the fact that I can almost never find the barrel I'm looking for at any of the stores I visit) but for some of us on another brand for us to switch it would have to cover what we have invested in the other brand – in a similar fashion to what photographers going to Nikon from Cannon consider in their lens collection

  • Richard Rhodes

    My home security system is a barky dog and a Mossberg 500 w/20" barrel.

  • William F. Gandel

    Why did Patrick Flanigan leave Winchester and stop promoting their X-3 and now hype the Mossburg "Rhythum 930"? Is the Mossburg a better shotgun or was it money?
    Many Thanks,

  • Alan_T

    I always liked the 500 ( except for the plastic safety button [ yes I know they make steal after market replacements ] ) . I might just have to aquire a new one .

  • Steve

    Ahhhhhhh, maybe a bit too"tricky dicky" for me. I have pistols that will shoot one half inch groups at 25 yards, and I have pistols that will shoot 2 inch groups but are super reliable. The last are the ones I carry. If you could "switch" them around, which state would you leave them in? I have rifles that will do 1/2 inch and one that will do 1/4 inch and I have semi .223's that will do 1 1/4 to 2 1/2 inches. Same question about "switching" around. I have some real classic shotguns that are for clay birds normally. I do have a mossberg 500 that has ghost ring sights and really loves .65 caliber single round ball slugs. I have tortured (not "torture tested") two Mossberg 500's in my career. I mean I really tried to make them come unglued. And not for a few days or a week or a month. I even shot them (with a remote cord) with the barrels loose. However if someone wants to own only one gun, maybe for economics, or just not interested in others, I guess more power to them.

    • Snug

      There is one thing you have not considered. When the British disarmed their subjects tho last firearm barred from ownership was the shotgun.
      Remember that and vote accordingly …..NO Democrat or Rino gungrabbers!

  • Jon

    Versatility and the ability to cater ,or customize,a weapon to be attractive to a large group as a packaged item,is really putting it all on the line and i give the company credit in these times for doing it.

  • Ken Barnes

    Not really a new idea for Mossberg. They have been this way since they came on the market. The interchangeable barrels and all the aftermarket goodies are what drew me to them years ago. Plus the price. I own the Model 500 in 12 gauge (2 of those), 20 gauge and even .410. They are reliable, accurate and inexpensive. I've had one of them for over 30 years with three barrels, pistol grip and recently added the adjustable stock. It's my "house gun with 18" barrel. The second 12 and the 20 gauge are set up for deer with rifled, ported barrels and scopes. The .410 is my squirrel gun. The package deals have always been out there too, maybe not to the extent that they are now. Bought most of mine that way. They make a nice bolt action rifle too, with the Lightning trigger, mine is in 30-06 and is a very nice gun for the money spent. Less than $350 with 3x9x40 scope included. I'm a big Mossberg fan, probably couldn't tell that from my comments.

  • Hercammer

    hehehe…..Canadian 1962 870 20" from K ingston Penetentiary Guard Gun ….dont need 3 inch in the house

    baby smooth action…years of loading and unloading …my best grouse gun…and now..but .i see another gun in my

    future collection Damn You Mossberg !!!!!!!! heheheh

  • JMAC

    I have the Mossberg 500 pump for and folks with a poor attitude and an old bolt-action turkey gun for hunting. Got it from an old timer who bought it new in the early 60's. Great gun.

  • Michael P. Gucciard

    This appears to be a very interesting shotgun. I belong to a small segment of shotgun users who shoot "games". (Don't confuse with 3 gun.) I am curious whether Mossberg has considered providing a 30" barrel for this series. As a group, game shooters use a lot of pump shotguns. Winchester model 12 being the most used, Remington some, and Mossberg almost never. If this gun is built to stand up to the hard usage it it would get in trap & game shooting, a flexible platform like this might provve to be very appealing. Generally recreational shooters in this category are somewhat frugel, like to hunt, are serious about home protection, and shoot lots of ammunition.

  • Ramon Martinez

    i have a mossberg 500 tactical i usually use it as a home defense weapon but i wouldnt trade it for anything it has never failed to shoot and with a nebo protec light on the end anybody would run from it.!!

  • BadAssBass

    I grew up with guns, shot skeet with rentals and borrowed but never owned one. I would shop, look and compare but never pulled the trigger on a purchase, if you'll pardon the pun. I didn't want to get caught up in the collection syndrome. I have brothers that own between 30 to 60 long arms each. But the flex system sold me. Purchased the general purpose model plus the 18.5 barrel; the tactical forearm; a Streamlight (want to know what I'm shooting at even if something does go bump at 3 am. Also, the Shotlock solo-vault gave me quick access while securing the gun from any youngsters that might visit when I'm not around.

    Now, I have an HD weapon, a sport gun for skeet ( I LIKE shooting skeet with a pump) and later, I'll get the rifled slug barrel for hunting. I can literally change from field configuration to a tactical weapon in less than two minutes.

    Way Cool, Mossberg!

  • John Powers

    I am a sea kayaker who paddles the B.C. Coast, where bears can be a problem. I've been interested in a Mossberg with a short barrel and their marinecote feasture, but can no longer find any of their models with marinecote on their web page. Have they ceased to offer this option? If so, why? Do they have a saltwater-resistent alternative, or am I SOL?

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