.22 caliber

22 caliber, or 5.6mm caliber, refers to a common firearms bore diameter of 0.22 inch (5.6 mm).
Cartridges in this caliber include the very widely used .22 Long Rifle and .223 Remington / 5.56×45mm NATO.
.22 inch is also a popular air gun pellet caliber, second only to the ubiquitous .177 caliber.
Rimfire.
.22-inch caliber rimfire variations include:
Centerfire.
.22-inch caliber centerfire cartridges include: