The Glock G22 is chambered in 40 caliber. It is the most popular pistol used by police agencies in the United States. The reasons for the 60 to 70% popularity by law enforcement are: (1) Thirteen round standard magazines versus ten round magazines for 45ACP. (2) Less recoil than a 45ACP round. (3) More stopping power than a 9MM with minor increase in recoil. I purchased my Glock 22 when ammo was very expensive and hard to get. Now, since ammo is plentiful, the 40 is very close to the 45ACP in price, and the 9MM ammo is a bargain. The 40 caliber has been in existence since 1990. I posted a little history from the Glock website and two videos from You Tube by Hickok45.
The GLOCK 22 Gen4, in .40, introduces revolutionary design changes to this model of perfection that the majority of law enforcement across the country put their trust in every day. The Modular Back Strap design of the G22 Gen4 lets you instantly customize its grip to adapt to an individual shooter’s hand size. The surface of the frame employs the new scientifically designed, real-world-tested, Gen4 rough textured technology. Internally, the new GLOCK dual recoil spring assembly substantially increases the life of the system. A reversible enlarged magazine catch, changeable in seconds, accommodates left or right-handed operators. The G22 Gen4 .40 caliber retains the GLOCK accessory rail for your attachments.