Mossberg FLEX Modular 500/590 Shotguns – How Does It Work?

The Mossberg FLEX system is a catalog of optional accessories for the FLEX line of 500 and 590 pump shotguns. Each gun comes with a base set of equipment, and right now on the market you’ll see everything from this basic Cruiser with a breacher barrel, right up to 28″ vent rib duck guns in full camo. We didn’t get the camo components, but from this picture you can get an idea for the different options available. Note the short length of pull on the short stock, and the variations in recoil pads. This is a truly “FLEX’able” system for the greatest pump shotgun ever made.
Obviously the the part of the FLEX that everyone wants to know about is the swapping out of buttstocks at the wrist of the shotgun. This is how it comes apart, and the design seems to be solid as a rock under recoil.
The forend removes with a plastic button built into the mechanism. See below for more pictures of how it works.
The straight stocks come with a FLEX removable recoil pad system. You just pinch the end and they swap right out.
The only complaint we had with this design is the collapsible stock. Under heavy buckshot recoil it does a number on your cheek. The position of the 6 didn’t seem to matter.

Mossberg FLEX Shotguns

In a perfect world one gun will do everything you need. Well, the world isn’t perfect and who really only wants only one gun anyway? But a little FLEX’ability never hurts. When President Obama talked about people clinging to religion and guns, the gun he was probably talking about was the Mossberg 500 shotgun. If you are going to cling to a gun, the 500 isn’t the worst choice you could make, and it is probably the best. Last year Mossberg came out with a new addition to the 500 line, called FLEX, and it is indeed meant to bring a certain “FLEX’ability” to your Mossberg. At first glance you might think the various accessories in the pictures just screw on and off like normal hardware, but they do not. The FLEX system, in this first incarnation, is made up of three linkage systems. One is on the forend. Another is on the wrist of the gun, where the stock connects, and the third is on the butt of the stocks. With the FLEX system, one Mossberg 500 can be converted from a full length duck gun to a tricked out tactical to a bare bones pistol grip in about 30 seconds. Different recoil pads adapt for different sized shooters, and it takes no tools whatsoever to change the parts. Both the 500 and 590 guns are out in the market as FLEX guns, and they retail in the $450-$550 range depending on configuration.

At the heart of FLEX is the linkage at the wrist where you disconnect the rear stock. If there would be a weak point to the system, it would be this linkage, but after numerous attempts to get it to fail, the new design seems to be solid as a rock. When you first get the gun, whatever stock you got with it will be attached, and getting it off that first time is a little sticky, and you will probably be afraid of breaking it. Fortunately it is a painfully simple design, and appears to be very difficult to break. The T handle slides up. You turn it sideways, and the stock comes right off. Fitting a different stock is just as simple. You push it on, turn the handle and push it down. No tools, no problems, surprisingly easy. If you try to put the new one on cockeyed or upside down it doesn’t work. And after over 100 rounds of full snot buckshot, it didn’t loosen up at all, and because the locking system is all metal to metal, most likely thousands of rounds later it still wont’ loosen up.

Not less important but certainly less suspect is the forend switching mechanism. This is made from plastic, because it takes a lot less abuse than the wrist of the gun. We were sent a tri-rail forend in addition to the regular round FLEX version of the Mossberg forend that came on the stock Cruiser 500. You would expect the first version of a tri-rail to be somewhat gimmicky, but it is anything but. The rear of the grip is embedded with two rubberized pads that stick into their recessed slots with heavy duty Velcro. On the front left and right sides are two short rails for lights and lasers, and the bottom longer rail is removable. This gives you the option of making the overall grip thinner if you don’t choose to put a front handle on the forend. Because unlike many of the imitations, the Mossberg 500 action is short and smooth, and you don’t need the extra weight and encumbrance of a handle to rack the action.

The third FLEX’able component is the recoil pad. This may not seem like a big deal, but it is the most important swap out feature on the whole gun. Length of pull directly effects the way you hold a gun and the way you shoot a gun, and this effects how well you shoot it. We were sent three different lengths of straight stocks, and three different recoil pad thicknesses. That gives you the freedom to select a shorter stock and thicker butpad for the same length of pull as a longer stock and thinner pad. What configuration would you use for duck hunting when you might hammer a dozen or more high brass 3” shells through your gun? What about deer hunting with a slug barrel? Home defense? Would you want a shorter stock to get it to your shoulder faster, or would you opt for the pistol grip with a front handle on the tri-rail? The possibilities are what the FLEX system is all about.

Our FLEX parts didn’t include the camo versions, but they are out in the market. Our only complaint with the gun was the 6 position AR-15 style stock. It was not pleasant to shoot with defense loads and hammered the shooters cheek pretty bad with the lip of the sliding buttstock. If you want an AR type stock on your Mossberg FLEX, but a different slide on back from Magpul or something. The stock model isn’t comfortable. Is the Mossberg FLEX a revolutionary concept that will change the future of firearms? No, probably not. But what Mossberg did pull off is a pretty useful set of features, extremely well executed. The Mossberg 500/590 is the finest pump gun ever made, and no gun accumulation should be without one. With FLEX, you could buy a 16 year the gun with a few extra parts, and not only will he still be shooting it at 60, he will have been able to throw clay birds for both is kids and grandkids with the gun, without ever having to cut or replace a stock. That’s pretty cool.

FLEX requires no tools. The only sticky part of the system is removing the stock, but that is only because it is designed so that it never loosens up. The T handle never gets loose, yet is easy to lift, turn and lower, and all of the parts in the wrist are steel to steel. It isn’t shaky at all.
If you click this picture to make it larger you will see the way the linkage works. It is impossible to damage it by trying to insert it incorrectly.
The forend is a complete unit that operates by itself without the FLEX cover. Then you just choose which cover you want and they come on and off easy, and stay put securely.
This is the tri-rail forend. Those soft pads are inset and held by Velcro, so if you lose one it is easy to order a new one, unlike if they were glued in. The left and right light/laser rails are molded, but the bottom rail is removable for a thinner grip of you don’t want to mount a handle.
Our test gun came with Mossberg’s own patented version of the trigger paddle thingy, versions of which we find on bolt rifles, but you don’t see them on shotguns at all usually. They call it the LPA™ or Lightning Pump Action™, and it is a newly patented and somewhat revolutionary trigger when it comes to shotguns. This new series of 500 guns are a first for pump-action shotguns because the LPA trigger is user-adjustable from 3 to 8 pounds with an Allen wrench. This provides a rifle-like, creep-free trigger pull. The advantage of all the trigger paddle system is that you can set your trigger at a fairly light pull, and the device protects you from accidental discharges should you drop the gun. Our test gun also has the standard 500 tang safety.
This door breaching barrel is available as a barrel from the Mossberg store, as are all other Mossberg barrels.
The new Mossberg pistol grips shoots really well and is much more comfortable than the solid plastic one.
It never hurts to mention that even though there are now a lot of black pump shotguns on the market, they are not created alike. Even the guns from Turkey and other countries that operate similarly to the way a Mossberg works, there is no equal to the Mossberg 500 series, Made in the USA.

{ 12 comments… add one }
  • Mike March 16, 2014, 3:39 pm

    I have bought one of there just a few weeks ago and took it out to the range. I must say I am very impressed with this gun. I got this shotgun just for home defense and from what I have seen while ptting it though real life trials it is a great gun and I can move though small tight places with ease. Also with the interchangable parts I can customize this gun to my own needs. I recomend this gun to anyone who is looking for a home defense gun. I love it and its great.

  • Gunslinger February 27, 2014, 10:08 am

    Wonder how soon Mossberg will be leaving that facist state?

  • Dave December 25, 2013, 10:59 am

    As a JB Hunt truck driver, I have travelled down Interstate 91 many times and I have noticed the Marlin Factory on the Northbound side. I was wondering if the Mossburg shotguns come from this facility……?
    I am definitely getting the pistol grip 500 ………….it’s short and sweet …….it will handle target acquisition faster than my Pardner H&R……
    In my research of gun factories, I am amazed at how many there are in the New England States…..
    I am I love with Texas built Bond derringers, but damn they are expensive..!!!!!!!!!
    Go Cowboys and The NE Patriots………!!!!!!!
    PS I love my Hi-Point 9mm’s………..carbines and C9’s……………well built and as the saying goes bulletproof …..

  • Dave December 25, 2013, 10:51 am

    As a JB Hunt truck driver, I have travelled down Interstate 91 many times and I have noticed the Marlin Factory on the Northbound side. I was wondering if the Mossburg shotguns come from this facility……?

  • Steve Dunnington October 17, 2013, 1:18 pm

    This is pretty incredible. My favorite part is that it takes no tools to change the parts. Thanks for the very detailed post.

  • Jim Giunta October 7, 2013, 9:31 am

    Can this flex piece be fitted at the wrist to an older 500, or is this only available on new models?

    • Administrator October 7, 2013, 9:37 am

      It appears to not able to be retrofitted to old guns, but I suspect they will come out with adapters at some point.

  • donald October 7, 2013, 6:49 am

    great rifel…I have a 12 gage..pump..that is a it can go allday long… problem.

    • monster October 8, 2013, 7:20 am

      Yoo orta put them teef bak in yor haid afore yoo temt ta make corments heah donald!

    • Neil December 24, 2013, 1:04 am

      1. It is spelled RIFLE, not “RIFEL”
      2. This is a SHOTGUN, not a rifle!
      3. 12 gauge, not “12 gage”
      4. MossbERG, not “MossbURG” (it even says it in the title, and several places in the article)
      5. When you are joining two parts of a sentence, you use the AND, which is a conjunction, not “AN”, which is an article.
      6. All day is two words, not one!

      • bucketnumber6 December 25, 2013, 1:20 pm

        Using the FLEX grammer and spelling system?

    • robert June 22, 2015, 6:13 am

      I will stay with my Remington Vera Max! Shame On the spelling

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