.22 caliber

.22 caliber, or 5.6 mm, refers to a common firearms bore diameter of 0.22 inch (5.6 mm) in both rimfire and centerfire cartridges.

.22 inch is also a popular air gun pellet caliber, second only to the ubiquitous .177 caliber.

Rimfire

.22-inch caliber rimfire variations include:

.22 Long, a cartridge predating the .22 LR, with the same case length using the lighter .22 short bullet
.22 Long Rifle (LR), the most common cartridge type of this caliber, often referred to simply as ".22 caliber" or "22".
.22 Long Rifle Extra Long (LR EX), a variant of .22LR with a longer casing but identical overall cartridge dimensions (see CCI Stinger)
.22 Short, a cartridge used mostly in pocket pistols and mini-revolvers
.22 Winchester Magnum Rimfire (WMR), a magnum cartridge that is longer and more powerful than the .22 LR
.22 Winchester Rimfire (WRF), a cartridge originally introduced to provide higher velocity than the .22 LR

.22 Extra Long, a cartridge predating the .22 LR, not offered commercially since 1935
.22 Winchester Automatic, a cartridge specific to the Winchester Model 1903 rifle

.22 BB (Bulleted Breech Cap), a low-velocity cartridge with a case shorter than the 22 short
.22 CB (Conical Bullet Cap), a low-velocity cartridge with a case shorter than the 22 short
Quiet-22 (40 Grain lead projectile), a low-velocity cartridge with the same case as the .22 LR

.22-inch caliber centerfire cartridges include:

.22 Accelerator, a special loading of the .30-30, .308, and .30-06 cartridges that is manufactured by Remington
.22 BR Remington, a wildcat cartridge commonly used in varmint hunting and benchrest shooting
.22 CHeetah, a cartridge based on the Remington 308 BR, modified to .22 caliber
.22 Eargesplitten Loudenboomer, a cartridge based on a .378 Weatherby Magnum case intended to deliver high muzzle velocity
.22 Hornet (5.6×36mmR), a powerful cartridge variant introduced in 1930
.22 Nosler, a cartridge introduced in 2017 intended for use in AR-15-style rifles
.22 PPC, a firearm cartridge used primarily in benchrest shooting
.22 Remington Jet, a cartridge designed for the Smith & Wesson Model 53 revolver
.22 Savage Hi-Power (5.6×52mmR), a cartridge introduced by Savage in 1912 for use in the Savage Model 99 rifle
.22 TCM (22 Micro-Mag), a shortened .223 Remington case designed to load into standard 9mm pistol magazines
.22 Winchester Centerfire (WCF), a cartridge introduced in 1885 for use in a Winchester single-shot rifle
.22-250 Remington, a very high velocity cartridge

.220 Rook (.220 Long Centrefire), an obsolete British cartridge of the 1880s
.220 Russian (5.6×39mm), a 7.62×39mm cartridge necked down to hold a 5.6 mm bullet
.220 Swift (5.56×56mmSR), the first cartridge (1935) with a muzzle velocity of over 4,000 ft/s (1,200 m/s)

.221 Remington Fireball, a special cartridge for use in the experimental XP-100 pistol (1963)

.222 Remington, the first commercial rimless .22 (5.56 mm) cartridge made in the United States (1950)
.222 Remington Magnum, a short-lived commercially produced cartridge derived from the .222 Remington
.222 Rimmed, an Australian cartridge of the 1960s for single-shot rifles

.223 Remington, a commercial cartridge developed for the ArmaLite AR-15, from which the 5.56×45mm NATO cartridge was derived
.223 Winchester Super Short Magnum (WSSM, 5.56×42mm), a cartridge based on the Winchester Short Magnum case

.22 Spitfire (5.7mm Johnson, originally MMJ 5.7), a cartridge introduced in 1963 for .224 cal. re-barreled or lined US 30 Carbines
.224 Weatherby Magnum (5.56×49mmB), a cartridge developed in 1963 for use in the Weatherby Varmintmaster rifle
.224 Boz, a cartridge developed in the late 1990s, intended to defeat body armor
.224 Valkyrie (5.6×41mm), a cartridge similar to the 5.56×45mm NATO, with a shorter case length
.224-32 FA, a cartridge designed in 2009 for use in the Freedom Arms Model 97 revolver