The MP22 Carbine is based off the AR-15 platform. But it uses a short stroke piston and it has a collapsible wired stock. It shoots the .22LR caliber.
Designer: Michael Smith
Year Designed: 1970s-1980s
Rate of Fire: ~500-600 RPM
Muzzle velocity: 1,200ft/s (366 m/s)
The MP22 Carbine was developed by Michael Smith in the National Armory in Springfield. He notice that the AR-15 and even the AR-15 carbine was too big for law agencies fighting in extreme tight CQB. So he developed the MP22 in request of the LCPD in the early 1970s. By 1985, the MP22 was finish from the proto type stages and ready to enter service. The LCPD adopted it in the 1990s. But, it was replace in a more bigger hitting SMG (the MP5) in the early 2000s. Although the MP22 was perfect for CQB, but the cons of this SMG was it shoots a very weak .22LR cartridge. It failed to penetrate body armour and even thick clothings.