A musket is a muzzle-loaded, smoothbore firearm, fired from the shoulder. Muskets were designed for use by infantry. A soldier armed with a musket had the designation musketman or musketeer.
The musket replaced the arquebus, and was in turn replaced by the rifle (in both cases, after a long period of coexistence). The term "musket" is applied to a variety of weapons, including the long, heavy guns with matchlock, wheel lock or flint lock and loose powder fired with the gun barrel resting on a stand, and also lighter weapons with a snaphance, flintlock, or caplock and bullets using a stabilizing spin (Minié ball), affixed with a bayonet.
The musket first made its appearance when a specialist class of troops armed with a heavy version of the arquebus called a musketin was introduced to support the arquebusiers and pikemen in the Spanish tercios. By the end of the 17th century, a lighter version of the musket had edged out the arquebus, and the addition of the bayonet edged out the pike, and almost all infantry became musketeers.
In the 18th century, improvements in ammunition and firing methods allowed rifling to be practical for military use, and the term "rifled gun" gave way to "rifle". In the 19th century, rifled muskets (which were technically rifles, but were referred to as muskets) became common, combining the advantages of rifles and muskets. About the time of the introduction of cartridge, breechloading, and multiple rounds of ammunition just a few years later, muskets fell out of fashion.
Musket calibers ranged from 0.50 to 0.75 in (13 to 19 mm). A typical smooth bore musket firing at a single man-sized target was only accurate to about 40 to 50 yd (37 to 46 m) using the military ammunition of the day, which used a much smaller bullet than the musket bore to compensate for accumulation of ash in the barrel under battlefield conditions. Rifled muskets of the mid-19th century, like the Springfield Model 1861, were significantly more accurate, with the ability to hit a man sized target at a distance of 500 yards (460 m) or more. The advantage of this extended range was demonstrated at the Battle of Four Lakes, where Springfield Model 1855 rifled muskets inflicted heavy casualties among the Indian warriors before they could get their smooth bore muskets into range. However, in the Italian War of 1859, French forces were able to defeat the longer range of Austrian rifle muskets by aggressive skirmishing and rapid bayonet assaults during close quarters combat.