Volley gun
The Ribauldequin was a medieval version of the volley gun. It had its barrels set up in parallel. This early version was first employed during the Hundred Years' War by the army of Edward III of England, in 1339. Later on, the late Swiss army employed it.
Musket
The invention of the Minié ball in 1849 solved both major problems of muzzle-loading rifles. The Crimean War (1853–1856) saw the first widespread use of the rifled musket for the common infantryman and by the time of the American Civil War (1860s) most infantry were equipped with the rifled musket. These were far more accurate than smoothbore muskets and had a far longer range, while preserving the musket's comparatively faster reloading rate. Their use led to a decline in the use of massed attacking formations, as these formations were too vulnerable to the accurate, long-range fire a rifle could produce. In particular, attacking troops were within range of the defenders for a longer period of time, and the defenders could also fire at them more quickly than before. As a result, while 18th century attackers would only be within range of the defenders' weapons for the time it would take to fire a few shots, late 19th century attackers might suffer dozens of volleys before they drew close to the defenders, with correspondingly high casualty rates. However, the use of massed attacks on fortified positions did not vanish overnight, and as a result, major wars of the late 19th century and early 20th century tended to produce very high casualty figures. Nevertheless, the smoothbore musket was still a formidable weapon in medium and short distances. The general shooting distance was well within the effective range of the old smooth bore muskets, especially in the first years of the war. Neither the officers nor the soldiers received proper training to take advantage of the accurate long range fire of the rifle musket. The volleys were fired from a distance where it was possible to see the white of the eye of the enemy. Within this 100 yard distance the effectiveness of the rifle musket was not more than the effectiveness of the smooth bores. In fact the buck and ball loads proved more effective in many occasions. The Irish Brigade chose to keep their U.S. 1842 muskets, and used them with deadly effect at the battles of Antietam and of Gettysburg. The buck and ball was a better choice also when the untrained soldier felt the first stress of the battle and had to aim and fire rapidly through heavy smoke on an enemy advancing fast. Stopping a cavalry charge with single ball or Minié bullet is much harder than firing a volley with muskets loaded with buck and ball.