Editing Rifle (section)

===Caliber===

Rifles may be chambered in a variety of [[caliber]]s (bullet or barrel diameters), from as low as 4.4&nbsp;mm ([[.17 HMR|.17]] inch) [[Varmint rifle|varmint]] calibers to as high as [[20 mm caliber|20 mm]] (.80 caliber) in the case of the largest anti-tank rifles. The term [[caliber]] essentially refers to the width of the bullet fired through a rifle's barrel. Armies have consistently attempted to find and procure the most lethal and accurate caliber for their firearms.

The standard calibers used by the world's militaries tend to follow worldwide trends. These trends have significantly changed during the centuries of firearm design and re-design. Muskets were normally chambered for large calibers, such as .50 or .59 (12.7&nbsp;mm or 15&nbsp;mm), with the theory that these large bullets caused the most damage.

During World War I and II, most rifles were chambered in .30 caliber (7.62&nbsp;mm), a combination of power and speed. Examples would be the [[.303 British]] [[Lee–Enfield]], the American [[M1903 Springfield|M1903]] [[.30-06 Springfield|.30-06]], and the German [[Karabiner 98k|8mm Mauser K98]].

An exception was the Italian [[Carcano|Modello 91]] rifle, which used the [[6.5×52mm Mannlicher–Carcano]] cartridge.

Detailed study of infantry combat during and after World War II revealed that most small-arms engagements occurred within 100 meters, meaning that the power and range of the traditional .30-caliber weapons (designed for engagements at 500 meters and beyond) were essentially wasted. The single greatest predictor of an individual soldier's combat effectiveness was the number of rounds he fired. Weapons designers and strategists realized that service rifles firing smaller-caliber projectiles would allow troops to carry far more ammunition for the same weight. The lower recoil and more generous magazine capacities of small-caliber weapons also allow troops a much greater volume of fire, compared to historical [[battle rifles]]. Smaller, faster traveling, less stable projectiles have also demonstrated greater terminal ballistics and therein, a greater lethality than traditional .30-caliber rounds. Most modern service rifles fire a projectile of approximately 5.56&nbsp;mm. Examples of firearms in this range are the American [[5.56×45mm NATO|5.56&nbsp;mm]] [[M16 rifle|M16]] and the Russian [[5.45×39mm]] [[AK-74]].