The .22 long rifle rimfire cartridge is a long established variety of ammunition, and in terms of units sold is still by far the most common in the world today.
The cartridge is often referred to simply as .22 LR and various rifles, pistols, revolvers, and even some smoothbore shotguns have been manufactured in this caliber. The cartridge originated from the Flobert BB cap of 1845 through the .22 Smith & Wesson cartridge of 1857, and was developed by the American firearms manufacturer J. Stevens Arms & Tool Company in 1887 by combining the casing of the .22 long with the 40-grain (2.6 g) bullet of the .22 extra long. For many decades, it has been a very popular cartridge around the world. It is one of the few cartridges that are accepted by a large variety of rifles, as well as pistols. The .22 long rifle and related cartridges (.22 short, .22 long, and .22 extra long) use a heeled bullet, which means that the bullet is the same diameter as the case, and has a narrower "heel" portion that fits in the case.
Low cost, minimal recoil, and relatively low noise make the .22 LR an ideal cartridge for recreational shooting, initial firearms training, small-game hunting and pest control. Used by Boy Scouts for the rifle shooting merit badge, the .22 LR is popular among novice shooters and experts alike. The rimfire round is commonly packaged in boxes of 50 or 100 rounds, and are often sold by the ‘brick’, a carton containing either 10 boxes of 50 rounds or loose cartridges totaling 500 rounds, or the ‘case’ containing 10 bricks totaling 5,000 rounds.
A wide variety of rimfire ammunition is available commercially, and the available ammunition varies widely both in price and performance. Bullet weights among commercially available ammunition range from 20 to 60 grains, and velocities vary from 575 to 1,750 fts. Promotional loads for plinking can be purchased in bulk for significantly less cost than precision target rounds. The low cost of ammunition has a substantial effect on the popularity of the .22 LR. For this reason, rimfire cartridges are commonly used for target practice.
The low recoil of the .22 LR cartridge makes it ideal for introductory firearms courses. Novice shooters can be surprised or frightened by the recoil of more powerful rounds. Beginners shooting firearms beyond their comfort level frequently develop a habit of flinching in an attempt to counter anticipated recoil. The resulting habit impedes correct posture and follow-through at the most critical phase of the shot and is difficult to correct. With high recoil eliminated, other errors in marksmanship technique are easier to identify and correct.
Performance varies between barrel length and the type of action. For example, bolt-action rifles may perform differently from semiautomatic rifles. The .22 LR is effective to 150 yds, though practical ranges tend to be within 100 yds. After 150 yds, the ballistics of the round are such that it will be difficult to compensate for the large "drop". The relatively short effective range, low report, and light recoil has made it a favorite for use as a target-practice cartridge. The accuracy of the cartridge is good, but not exceptional; various cartridges are capable of the same or better accuracy. A contributing factor in rifles is the transition of even a high-velocity cartridge projectile from supersonic to subsonic within 100 yds. As the bullet slows, the shock wave caused by supersonic travel overtakes the bullet and can disrupt its flight path, causing minor but measurable inaccuracies.
When zeroed for 100 yds, the arc-trajectory of the standard high-velocity .22 LR with a 40-gr bullet has a 2.7-inch rise at 50 yds, and a 10.8-in drop at 150 yds.A .22 LR rifle needs to be zeroed for 75 yds to avoid overshooting small animals like squirrels at intermediate distances.
As a hunting cartridge, rimfires are mainly used to kill small game. It is highly effective on squirrels and rabbits at distances closer than 150 yds and on ground hogs, marmots, and foxes closer than 80 yds. It has been successfully used on larger animals such as coyotes, but range is generally limited to no farther than 65 yds; head and chest shots are preferred with the most powerful .22 cartridge the hunter can use accurately.
Because a .22 LR bullet is less powerful than larger cartridges, its danger to humans is often underestimated. In fact, a .22 LR bullet is capable of inflicting very serious injuries (e.g. the four people wounded, one mortally, during the Reagan assassination attempt) or death e.g. the Kauhajoki school shooting (11 killed and one wounded), the Jokela school shooting (eight killed and one wounded), and the 1979 Cleveland Elementary School shooting (two killed and nine wounded), as well as the assassination of Robert F. Kennedy. Numerous other shooting incidents have demonstrated that .22 LR bullets can easily kill or seriously injure humans. Even after flying 400 yds, a .22 bullet is still traveling about 500 fts. Ricochets are more common in .22 LR projectiles than for more powerful cartridges as the combination of unjacketed lead and moderate velocities allows the projectile to deflect – not penetrate or disintegrate, when hitting hard objects at a glancing angle. A .22 LR can ricochet off the surface of water at a low angle of aim. Severe injury may result to a person or object in the line of fire on the opposite shore, several hundred yards away.