The Many Faces of “FLEX”

Mossberg’s Plinkster Gets The Modular Treatment.

By Holt Bodinson

If you’re into AR’s and are accustomed to swapping out uppers, buttstocks, handguards, sighting systems and flash suppressors, you can appreciate just how modular the world of firearms is rapidly becoming. The key phrase today is “form follows function.” Mossberg is just now fielding a thoroughly modular, autoloading, .22 rimfire rifle in their “Plinkster” series with a fascinating array of low-cost optional assemblies to convert it from a sporter into a racy AR-looking tactical model, or from an adult-size rifle to a youth-size one in a matter of seconds. The secret is Mossberg’s FLEX system.

Mossberg’s quick-change, modular system, called “FLEX,” was developed originally by Mossberg engineers for a military application. The military had made it be known they were interested in a modular shogun. Mossberg’s rugged and utterly reliable Model 590A1 pump gun had been the US military’s primary fighting shotgun for three decades so Mossberg moved vigorously ahead to design a modular shotgun system to keep them in first place for the next three decades. Then, unfortunately, military budgets and procurement programs tightened up. Not wanting to waste the investment made in developing the FLEX system, Mossberg brought it over into their sporting and tactical lines.


What unlocks Mossberg’s “Tool-Less Locking System” is this integral
key in the stock wrist (above). The splined stub at the end of the
receiver is mated with a female socket in the stock (below).



The FLEX autoloaders will accept both a 10-shot and a 25-shot magazine.

First FLEX

Initially, the FLEX system and accessories appeared in the Model 500 and 590 shotgun series. The system proved so successful it was then extended into the tactical bolt-action and lever-action rifle lines. The rimfire lines simply had to follow. With much thanks to Linda Powell of Mossberg, the FLEX Plinkster pictured here is the original prototype for a new Plinkster rimfire FLEX line that should be appearing at your dealers as you read this.

The key to the FLEX system is its “Tool-less Locking System” that goes by the acronym, “TLS.” What the TLS provides the rimfire shooter is a quick and convenient way to change out a variety of low-priced, fixed and adjustable stocks, combs and recoil pads, virtually in seconds.

It’s a mix-and-match game, and once you’ve begun to play, it becomes addictive.


In its tactical dress, the FLEX Plinkster makes quite an impression.
The tactical model is dressed up with an A2-type flash hider and
fiber optic sights.


Converted into a classy sporter, the FLEX Plinkster
transforms into a perfect small game rifle.


The TLS is the coupling system connecting the receiver to the buttstock. There is no longer a long through-bolt hidden under the recoil pad. In its place is a multi-splined stub at the rear of the receiver, which mates with a female socket in the wrist of the stock. Locking them together is a vertical, swiveling key recessed into the wrist of the buttstock.

In practice, all you have to do to change out stocks is to lift up the recessed TLS key, turn it 90 degrees counterclockwise, rap once with your hand on top of the comb (yes, the zinc-to-zinc joint is grabby) and then pull the receiver and existing stock apart.

To complete the changeover, you insert the new stock onto the receiver spline, turn the key clockwise and push it down. The result is a strong, rigid, metal-to-metal joint and a different model rifle or shotgun.

Mossberg’s Plinkster is the workhorse of their rimfire autoloading line. It’s been around a long time. It’s been thoroughly de-bugged. It just shoots and shoots without any fuss whatsoever. At last count, there were nine models in the Plinkster autoloading line with enough variations among them to please even the most fickle consumer. The line offers camouflaged stocks, pink marbled stocks, black synthetic stocks, wood stocks, thumbhole tipdown stocks, 18-inch barrels, 21-inch barrels, blue finishes, brush chrome finishes, 10- and 25-round magazines. There’s even a package with a factory-mounted 4X scope.

Now there’s a FLEX model—actually two. One is a factory tactical model furnished with a 6-position adjustable AR-type stock, a 16.25-inch barrel mounted with an A2-style flash hider, receiver mounted Picatinny rail, adjustable fiber optic sights and a 25-round magazine. The catalogue designation is FLEX-22 Rifle-25 Round. The second model carries the moniker FLEX-22 Youth Rifle. It’s supplied with fixed stock fitted with a 3/4-inch recoil pad giving an LOP of 13-1/4 inches (an alternative stock would be a compact model with an LOP of 12-1/2 inches), an 18-inch barrel, adjustable fiber optic sights and a 10-round magazine.

The prototype FLEX-22 arrived in a tactical format. With its 6-position stock, A2 flash hider, 25-round magazine and Picatinny rail, it’s a cool looking rifle. Not wanting to mount it with optics, I unscrewed the Picatinny rail from the receiver dovetail and plinked around using the open fiber optic sights. The 3-dot sight picture features a bright red dot cradled in between two green dots. It’s very visible and fast on target. I do like the 6-position stock with an LOP spanning from 11 inches to 14-1/4 inches. Yet, I wanted to see how the FLEX-22 would look and perform as a sporter. The transformation was easy and fast.

For a new buttstock, I selected what I consider the most flexible of all FLEX stocks. It’s Mossberg’s FLEX 4-Position, Adjustable Sporting stock supplied with both high and low interchangeable combs. The stock offers an adjustable LOP from 12-3/4 inches to 14-5/8 inches and low and high combs which are held in place by a single Allen screw.

Wanting to test Bushnell’s new 2-7x32MM, AR/22 rimfire scope with its Drop Zone graduated reticle, target turrets and side parallax focus, I reinstalled the Picatinny rail and mounted the scope in Leupold quick detachable rings, installed the high comb on the FLEX 4-position stock and hit the range to see how the overall system would perform.


The interchangeable combs for the 4-position stock (above) are
secured by a single Allen bolt. Both FLEX-22 models sport fully
adjustable fiber optic sights (below).


What I especially like about the Bushnell AR/22 scope is its side focus parallax adjustment, which is critical for rimfire accuracy at extended distances and its reticle, calibrated for the drop of a high-speed .22 bullet from 50 to 125 yards in 25-yard increments. Essentially you sight-in at 50 yards at any power and then turn the power ring up to 7X to use the drop compensating reticle.

In their instructions, Bushnell doesn’t specify what high-speed bullet weight or velocity should be used so I arbitrarily selected my current favorite, CCI’s Mini-Mag with a 36-grain bullet at 1,260 fps. Since you have to set the scope anyway to 7X for the drop compensating reticle to work, I set it at 7X and sighted the FLEX-22 in at 50 yards. The FLEX-22 rewarded my choice in ammunition with nicely rounded 1-1/2-inch 5-shot groups. It was time to see how the AR/22 scope would perform at 100 yards.

A slight 3-to-9 o’clock breeze had picked up which can be tricky for rimfire riflemen shooting out at 100 yards. I held dead-on the Birchwood-Casey, 8-inch Shoot-N-C bull’s-eye. The bullets impacted perfectly in terms of elevation, which is a credit to Bushnell’s excellent AR/22 reticle system, but they also grouped 3 inches left of center due to the breeze. Typically, elevation doesn’t ruin your day, it’s windage!

Mossberg’s FLEX system applied to its rimfire line is a real plus for shooters. For a family, it could fill a very economical niche for all ages and purposes from children to adults, from plinking to small game hunting and more. Since all the FLEX accessories are universal and interchangeable, they can be transferred from rimfire to centerfire to shotgun in a matter of seconds. Being able to tailor a variety of firearms to you or your family’s specific requirements while saving considerable cash is a pretty hard combination to beat. That’s FLEX!

Autoloading Rifles
Maker: O.F. Mossberg & Sons, Inc.
7 Grasso Ave.
P.O. Box 497
New Haven, CT 06473
(800) 363-3555

Action Type: Semi-automatic, blowback
Caliber: .22 Long Rifle
Capacity: 10-shot and 25-shot magazines
Barrel Lengths: Tactical: 16-1/4 inches
Youth: 18 inches
Overall Lengths: Tactical: 33-1/4 inches, collapsed, Youth: 36-1/4 inches
Weights: Tactical 5-1/2 pounds, Youth: 5 pounds
Finish: Blue, Sights: Tactical: Picatinny rail + Fiber optic. Youth: Fiber optic
Flex Stocks: Tactical: 6-position synthetic, Youth: Fixed synthetic
Price: Tactical: $275, Youth: $261
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