Ammo & Gear Reviews

Gear Review: The Mossberg FLEX System

Mike Piccione Editor, Guns & Gear
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The FLEX System lets you accessorize your Mossberg 500 and 590 shotguns as true all-purpose guns.

The Mossberg FLEX System is a revolutionary new concept for accessorizing a Model 500 or 590 with stocks, fore-ends and recoil pads using its new Tool-less Locking System (TLS).

The fore-ends range from tactical railed fore-ends to various camouflage patterns so the Mossberg FLEX can be quickly configured for any application without the need of a tool. Further adjust the length-of-pull by choosing a Flex System recoil pad, allowing for a more custom fit depending on shooting applications, amount of outerwear and stature of the shooter.

The Mossberg TLS locking devices are designed to withstand hard-use, whether in service on the front line or in the hunting fields. The stocks and fore-ends will be available in black and camouflage patterns, including Realtree Max 4 and Mossy Oak Infinity. Another important component of the FLEX system is Mossberg’s extensive selection of barrels, all of which fit FLEX System models. They include short tactical barrels, vent rib skeet barrels, camouflaged waterfowl barrels and tight-choked turkey barrels.

The TLS in the FLEX stock consists of a half-moon shaped locking piece. It is flush fitting and slides into a recess in the wrist. To release the locking piece, pull it up and rotate it 90 degrees so it is perpendicular to the wrist. The latch is captured so it can’t be lost. Once that is done, the stock slides off to the rear. The rear of the receiver has a metal peg with six ridges that mates to corresponding recesses in the various FLEX system stocks. Six different stocks compatible with the FLEX system are available from Mossberg. They include fixed stocks in three different lengths-of-pull (14 ¼ , 13 ½ , 12 ½  inches); a six-position collapsible M4-style tactical stock with a separate pistol grip, a four-position hunting stock with an adjustable comb and a pistol grip without a stock in the style of the Mossberg Cruiser.

The fixed stocks and the four-position hunting stock also have an interchangeable recoil pad as part of Mossberg’s FLEX system. It can be removed by depressing two buttons on either side of the toe of the stock. To remove the recoil pad, press the buttons simultaneously with the thumb and forefinger and pull back on the recoil pad with the opposite hand. FLEX recoil pads are available in three different thicknesses, including small (¾ inch), medium (1 ¼ inch) and large (1 ½ inch). The FLEX recoil pads are made from a compressible synthetic material that helps cushion recoil.

The FLEX fore-end is something like a shell that attaches to an internal chassis. Flex fore-ends can be detached by pushing forward on the recessed button in the bottom of the fore-end. The top of the release button is dished so it is easier to manipulate. Once the button is pushed, the fore-end can be pulled down and off of its chassis. Two different types of fore-end are available for the FLEX system¾a standard model and a tactical model with three Picatinny rails and grooves for pressure pads to activate lights or lasers. The tactical model can also be fitted with a detachable “chainsaw” grip that aids a proper grip for breeching.

Mossberg’s goal with the FLEX was to create a modular system that was similar to what shooters can find in the AR-15-style rifle; wherein one lower receiver can provide a platform for a variety of special purpose uppers, such as tactical, varmint or rimfire. In much the same way, one FLEX shotgun receiver can serve as the basis for anything from a turkey gun to a deer gun or a pheasant gun. With most shotguns, it has always been easy to swap out barrels, but now with the FLEX system, stocks, fore-ends and buttpads can be swapped out without tools. One shotgun can be a turkey gun, a deer gun or a pheasant gun. With the tactical models in particular you can switch from a close-quarters shotgun to a breeching tool by swapping the collapsing stock for a pistol grip and adding a chainsaw grip to the fore-end and switching from a tactical barrel to one with a breeching muzzle. That’s not something that would need to be done on the fly, but it would certainly simplify the armorer’s job.

Mossberg representatives told me that the FLEX system adds about $60 to the price of a comparable 500 or 590. The idea is you’ll buy a Mossberg FLEX in one configuration and then buy alternate stocks, buttpads and fore-ends as accessories. Mossberg has developed its own line, but it is working with aftermarket suppliers who will develop stocks and fore-ends of their own that are compatible with the FLEX system.

I had a chance to try out the Mossberg FLEX at a shooting event in South Carolina last December. The Deer were uncooperative, but the pheasant and quail were numerous. Swapping out components proved to be very straightforward thanks to the well-thought-out Tool-less Locking System. The release buttons were very secure and preserved the natural lines of the gun, but most importantly, even though stocks and fore-ends and buttpads were swapped out frequently, the locking system betrayed no signs of looseness. From the beginning of the event to the end, the FLEX components remained tight. It appears to be a system with a lot of promise that is sure to go over well with shotgun enthusiasts, whether they are looking for a pump shotgun for hunting, competition or self-defense¾or especially if they looking for a shotgun to fulfill all of those needs.

Thanks to the staff at for sending us this gear review.