An extract on #arthelp
The Russo-Japanese War of 19041905 was the first modern war of the 20th century. Military observers from Great Britain, Germany, France, and the United States witnessed first hand the first major conflict fought with high velocity bolt-action rifles firing smokeless powder on a massive scale. The Battle of Mukden fought in 1905 consisted of nearly 343,000 Russian troops against over 281,000 Japanese troops. The Russian MosinNagant Model 1891 in 7.62mm was pitted against the Japanese Arisaka Type 30 bolt-action rifle in 6.5mm, each had velocities well over the 19th century black powder velocities of under 2,000 feet per second (610 m/s).
Until the late 19th century rifles tended to be very long, some rifles reaching approximately 2 m (6 ft) in length (see long rifle) to maximize accuracy, making early rifles impractical for use by cavalry. However, following the advent of smokeless powder which was as much more powerful, a shorter barrel did not impair accuracy as much. As a result, cavalry saw limited, but noteworthy, usage in 20th century conflicts.
The advent of massed, rapid firepower of the machine gun, submachine gun and the rifled artillery piece was so quick as to outstrip the development of any way to attack a trench defended by riflemen and machine gunners. The carnage of World War I was perhaps the greatest vindication and vilification of the rifle as a military weapon.
The M1 Garand was a semi-automatic rapid-fire rifle developed for modern warfare use in World War II.
During and after World War II it became accepted that most infantry engagements occur at ranges of less than 300 m; the range and power of the large full-powered rifle cartridges were "overkill"; and thus the weapons were heavier than ideal. This led to Germany's development of the 7.9233mm Kurz (short) round, the MKb-42, and ultimately, the assault rifle. Today, an infantryman's rifle is optimized for ranges of 300 m or less, and soldiers are trained to deliver individual rounds or bursts of fire within these distances. Typically, the application of accurate, long-range fire is the domain of the marksman and the sniper in warfare, and of enthusiastic target shooters in peacetime. The modern marksman rifle and sniper rifle are usually capable of accuracy better than 0.3 mrad at 100 yards (1 arcminute).
Rifles may be chambered in a variety of calibers, from as low as .17 (4.4mm) varmint calibers to as high as .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, with the theory that these large bullets caused the most damage.
During World War I and II, most rifles were chambered in .30 caliber, a combination of power and speed. Examples would be the .303 British LeeEnfield, the American M1903 .30-06, and the German 8mm Mauser K98.
An exception was the Italian Modello 91 rifle, which used the 6.552mm MannlicherCarcano cartridge.
Detailed study of infantry combat during and after WWII 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) was 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 allows 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 5.56mm. Examples of firearms in this range are the American 5.56 mm M16 and the Russian 5.4539mm AK-74.