One of the best things about the basic AR15 platform has been its adaptability to a wide range of cartridges beyond the original 5.56/.223. One of the most useful and popular adaptations of the AR15 has been to .22 LR cartridge. One of the best of that breed is the Smith and Wesson M&P15-22.
The M&P15-22 M4 style carbine exhibits all the features I feel are necessary for a.22 rimfire AR15. Not all .22LR M4 type carbines do.
A .22 caliber AR must be nearly indistinguishable in appearance and operating features from the actual centerfire AR15 that it emulates. While a .22 rimfire can't be a 100% dead ringer for its higher powered brother since the action is blowback operated, the rest of the rifle, including the controls, can.
AR15 controls are extremely intuitive in nature, and function in a format identical to a service type semi-automatic pistol. In order to fulfill the mission of a sub-caliber understudy or defensive arm, a .22 rimfire AR needs to be operated with the very same control system that centerfire ARs use, and in the same position, otherwise its overall value is compromised. Not all manufacturers understand that. Smith and Wesson does. The safety selector switch, charging handle, bolt release/lock and magazine release are in the same place and operate the same as centerfire ARs, and are Mil-Spec in operation, shape and design. The M&P15-22 needs no change in operating procedure. The stock is a military type M4 carbine stock and is fully adjustable. Other than a slightly lighter weight, you really can't tell the difference between it and a centerfire M4.
The upper and lower receivers and quad-rail forend of the M&P15-22 are made of heavy duty polymer which saves money and weight. The forend allows the mounting of any Picatinny rail ready accessories. Polymer construction readily lends itself to be carried in RVs, Jeeps, boats or the back of pickup trucks without concern for damage. Not only is this important for a sub-caliber understudy training arm, but it is a huge deal when the .22 LR M&P15-22 is used in a defensive role.
Not everyone enjoys shooting a centerfire rifle cartridge. Also, it is not always safe to launch 5.56 rounds in confined urban/suburban areas. The M&P15-22 gives you the option of using an M4 style firearm for self defense or predator control with decreased risk in populous areas. Its low recoil and noise level makes it much more pleasant for a new shooter to learn on before graduating to the 5.56 or other caliber AR. That new shooter may also decide to stick with the .22LR M&P15-22 as their own personal defensive arm. I have no problem with that!
When a dangerous criminal is faced with a law abiding citizen armed with the M&P15-22, I guarantee they will not note any difference between a decked out M&P15 in 5.56 and the .22 LR version, especially when it is equipped with a weapon light or laser sighting system. Besides, no one wants to be shot with a .22, especially one that has 25 rounds available for that purpose.
I test fired an M&P15-22 on the Vance Outdoors Shooting Range. When shooting an M4 style carbine like this from the standing position, one of the mistakes I sometimes see people making with it is firing it with the stock fully extended. This defeats the advantage of using an arm with a 16 inch barrel when doing things like checking your house and property. It makes it less maneuverable. When firing from standing, shorten the stock so that when mounted, your nose nearly touches the charging handle. You won't get banged. Extend the stock for a comfortable cheek weld when firing prone.
Loading the magazine was a snap. It was as easy to load at round 25 as it was a round 1. Using the factory sights at 30 feet, I was rewarded with a very nice cluster of rounds and the M&P15-22 shot right to the point of aim. Even if you purchase an optic, make sure you are competent in the use of the iron sights in case your optic goes down. Firing the M&P15-22 was fun. It was nice not to have a large level of muzzle blast for a change. There were no malfunctions-the M&P15-22 ran flawlessly even with a normal amount of "rental gun" fouling. The trigger was the standard military AR15 in terms of crispness and break, and was just what one would expect and want for a military style arm. I don't favor ultra-light triggers on this type of arm. You can deliver a lot of ammo downrange in a very short period of time-which is the fun part.
The M&P15-22 line features a wide variety of choices and variants. Currently there are 18 different models available, including California compliant models.