In 2011, Smith & Wesson introduced the M&P22, chambered in .22 Long Rifle. The internal construction and blow-back operation of this rim fire cartridge variant has many similarities to the Walther P22, as it is manufactured by Carl Walther GmbH (Germany) for its U.S. distributor, Smith & Wesson.
It is dimensionally identical to the M&P9 (9 mm). I have several of them with 100,000+ rounds thru them.
I was fully disassembling and cleaning one the other day and thought others might be interested in a couple of related issues.
First, the firing pin spring is located in a channel in the breech block (Sig-like), the firing pin is located by the breech block -slide retaining roll pin. The channel is slightly too wide which allows the firing pin spring to buckle at both ends during the internal hammer strike. This firing pin spring fractured @ 11,000 rounds. Easy to replace but I fabricated a brass guide rod for the spring, the length of which is precisely long enough to not allow spring buckling at its end and not interfere with function. Guide rods are used in many other firearm applications for the same intent, why not the step child M&P22?
However , in order to change out the firing pin spring the breech block has to be removed from the slide, easy!. Installing the breech block with a spring loaded extractor on its lateral surface is a gunsmithing cussing session. So, I fabricated a few methods to retain the extractor under tension for much easier
Installation assembly. Tie wraps initially, then a modified crescent wrench which is nirvana, transforming a cuss-laced task into a one-handed easy-peasy operation.
A short review of the M&P22 full size breech block anatomy, the spring fracture, the easy repair solutions.