Profoundly Rimfire

Profoundly Rimfire

Smith & Wesson's brand-new M&P15-22 is an honest-to-goodness .22 rimfire carbine.

The standard M&P15-22 (bottom) is offered with a six-position buttstock, mil-spec quad-rail handguard, adjustable sights, T/C-manufactured match-grade barrel, and 25-round magazine, or it can be equipped with Magpul accessories (above).

Smith & Wesson's new M&P15-22 is the first AR-15-format rifle to be designed and built as a dedicated, true .22 LR semiauto from the ground up, with all the standard operating features and accessory specifications of a modern-version centerfire AR-15. The result is a rifle that's a great all-purpose, lightweight, rimfire sporter and hunting tool that is also ready for serious use as a sub-caliber duty AR-15 training arm for law enforcement or citizen defense. For those who have long wished for a "real" .22 Long Rifle AR-15, it's a great step forward.


Of course, AR-15 .22 rimfire conversions and adaptations to the basic centerfire platform have been available since the AR-15 was first introduced more than a half-century ago, and they have always been popular and in great demand. Easy to install, such kits typically consist of a self-contained, direct-blowback action replacement with an integral chamber insert to replace the centerfire AR-15 bolt carrier assembly and a .22 LR magazine.

However, from the perspective of functional correspondence with a "real" AR-15, such kits have always had limitations. For one, conversion kit design requires the bullet to travel several inches in an unrifled tube before it reaches the barrel and engages the rifling, meaning it is highly unlikely it will be truly concentric with the bore when it gets there. Moreover, the rifling on most AR-15 rifles is typically optimized for the more popular bullet weights of .223 Remington/5.56mm NATO ammunition with a twist rate of 1:7 to 1:9, which is a far cry from the 1:16 twist that is optimum for a .22 LR. Even the "slow" 1:12 twist of very early generation AR-15s isn't appropriate. Plus, the true caliber diameter of .22 LR bullets is .222, while the caliber of .223/5.56mm centerfire bullets is .224, requiring the soft lead .22 LR bullet to deform under propellant gas pressure to fully engage a centerfire AR-15 bore. All of which means that the accuracy delivered by most AR-15 .22 rimfire conversion kits is inadequate for anything but busting dirt clods at close range.


Maintenance with an AR-15 .22 LR conversion kit is also a problem. Because of the much lesser gas pressure and heat generated by .22 LR ammunition, the gas tube of a centerfire AR-15 upper receiver tends to foul and even block with residue, requiring strict attention to cleaning before returning to centerfire use. The chamber-insert design of conversion kits results in increased action fouling as well, clogging extractors, preventing firm bolt seating, and causing light primer-indent misfires.


Even more important from a training point of view, no .22 LR conversion kit can operate the AR-15's bolt-lock feature, rendering it useless for real-world AR-15 training purposes. When the last round in a conversion kit magazine is fired, the returning bolt will either stop against the back of the magazine follower or will return to battery. To reload, the user then has to remove the magazine (which drops the bolt if it's resting against the magazine follower), insert a fresh magazine, and cycle the charging handle to chamber a fresh round. Because the bolt does not automatically lock open, there is no visual way for the user to check whether the magazine is really empty or an unfired round is still in the chamber, and standard AR-15 reload drills--which involve dropping a locked-back bolt with the receiver's bolt-release lever--are impossible.

Unlike AR-15 .22 LR conversion kits, the M&P15-22's bolt locks open after the last round in the magazine is fired, and the bolt release lever functions normally.

A True Rimfire AR
The new S&W M&P15-22 resolves all these problems--and more. Engineered and manufactured from the ground up as a true .22 LR AR-15 rifle, its operator mechanics and features are identical to a centerfire AR-15's. The boltstop works the same. The magazine release works the same. The two-position safety switch works the same. The standard equipment sights are positioned the same and operate the same. The charging handle works the same. It disassembles for maintenance the same. All accessory and attachment point specifications are the same. Just about everything is the same--except it's a .22 rimfire.

Of course, there are some elemental differences as well. Most notably, the M&P15-22's upper and lower receivers are fabricated from lightweight, high-strength, glass-filled, nylon polymer with integral steel inserts in appropriate stress and reinforcement points. The full-length quad-rail handguard is also polymer. The M&P15-22 therefore weighs notably less overall than a centerfire AR-15 and has faster handling qualities (particularly for younger and smaller sport shooters). A standard centerfire AR-15 in basic configuration weighs about 6.5 pounds. The M&P15-22 weighs a full pound less.

Also, the interface dimensions of the upper and lower receiver units are intentionally designed at a fraction less than 100 percent of centerfire specifications, as well as shorter overall, to make it impossible for anyone to install a standard AR-15 upper receiver on a polymer M&P15-22 lower receiver, or vice versa. And the upper receiver does not have a forward-assist lever; the straight-blowback action doesn't need one.

The M&P15-22's 16-inch barrel is manufactured by Thompson/Center and provides the superb accuracy for which that company's bores are renowned. The barrel/ejector assembly fits into a stainless-steel insert in the upper receiver and is held in place by an external locking nut, which also secures the free-float handguard. This system allows precise headspacing with the aluminum direct-blowback bolt and also means that the handguard is not detachable without removing the barrel, which requires a special tool. This also differs from the design of centerfire AR-15s.

The M&P15-22 can be quickly disassembled into its basic components exactly the same as a centerfire AR-15. Note the self-contained bolt and recoil spring assembly.

Otherwise, most features of the M&P15-22 are pure mil- spec. Disassembly mechanics are the same as a standard AR-15. The upper receiver has an A-3-style flat to

p with standard Picatinny crosscuts for mounting sights, optics, and accessories. The quad-rail handguard accepts any 1913 mil-std rail-adaptable accessories (lights, lasers, vertical foregrips, etc.), and the design allows for installation of forthcoming alternative configuration handguards for those who do not need quad-rail attachment points.

The rail-mounted military-style front and rear sights are fully adjustable, with dual apertures, and they are also made of polymer. The M&P15-22 comes with a standard A-2-type pistol grip and is designed to accept most standard aftermarket accessory AR-15 pistol grips.

The standard-version M&P15-22 features a six-position, collapsible stock fitted to the molded lower receiver's mil-spec-diameter solid extension tube, which will also accept any other aftermarket custom carbine stock.

And if you don't care for the standard AR-15-type 7-pound trigger on the gun, you can also install a match-grade aftermarket custom AR-15 trigger because the internal trigger group specs are also standard. One interesting design sidelight is that the M&P15-22's hammerspring is tuned specifically for rimfire ignition, thus eliminating the propensity of centerfire hammersprings to cause case-head ruptures, as occurs with some conversion kits.

M&P15-22 magazines feature ambidextrous, easy-load assist buttons and removable basepads for easy disassembly.

The gun will be issued with 25-round, solvent-impervious polymer magazines with ambidextrous load-assist buttons, which are S&W's own dedicated .22 LR design and material. Ten-round magazines will also be available for states where capacities are limited or for shooters who prefer them.

Recommended retail price? Only $499, which is about as much as the lowest quality .22 LR upper receiver replacement units now on the market for centerfire AR-15s.

A Sweet Shooter
I first had the opportunity to handle and fire--and fire, and fire, and fire--a prototype M&P15-22 early this year at the S&W factory prior to its formal introduction at the May NRA Annual Meetings in Phoenix, and I was immediately captivated. It's light, quick, accurate, reliable, and pure fun. A few months later Shooting Times was able to latch onto two production guns--one in standard format, the other accessorized with Magpul accessories and a Trijicon Reflex II fast-acquisition optical sight. I set the standard version up with a Leupold VX-III 2-8X 36mm scope with mil-spec rings.

Grabbing a box of CCI Mini-Mag .22 LR ammunition, I sat down at a 50-yard benchrest at PASA Park. Through the scope my first five-shot group looked to be just under an inch, so I couldn't help myself--I emptied the rest of the magazine. It chewed a single, ragged hole in the target that measured just 1.13 inches overall. That was 25 shots in less than the diameter of a walnut.

I completed a formal accuracy review for five .22 LR ammunition varieties with much the same result (see the chart on page 44), then turned to shooting with the accessorized M&P15-22 on PASA Park's .22 rimfire steel-target range, stopping only when I realized I had nearly exhausted my inventory of .22 LR ammunition and Smith & Wesson demanded the guns back so they could be shown to somebody else. I think I've found my next squirrel rifle.

I admit I'm an unapologetic AR-15 enthusiast, and ever since the U.S. Army first issued me an M-16 during basic training back in 1968, I've always wished for a true, dedicated rimfire version. This is it.

It's the most fun I've had with a .22 in more than 10 years.

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