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.
Combat shotgun
While the sporting shotgun traces its ancestry back to the fowling piece, which was a refinement of the smoothbore musket, the combat shotgun bears more kinship to the shorter blunderbuss. Invented in the 16th century by the Dutch, the blunderbuss was used through the 18th century in warfare by British, Austrian, Spanish (like the Escopeteros Voluntarios de Cadiz, formed in 1804 or the Compañía de Escopeteros de las Salinas, among others) and Prussian regiments, as well as in the American colonies. As use of the blunderbuss declined, the United States military began loading smaller lead shot (buckshot) in combination with their larger bullets, a combination known as "buck and ball". The buck and ball load was used extensively by Americans at the Battle of New Orleans in 1814 and was partially responsible for the disparate casualty rates between American and British forces. The advantage of this loading was that it had a greater chance of hitting the enemy, thus taking wounded soldiers out of a fight. The disadvantage of this load was that the buckshot did not cause as severe wounds at longer ranges, and contemporary accounts show many of the British wounded recovering quickly as they had been struck by the buckshot rather than the ball. Fowling pieces were commonly used by militias, for example during the Texas Revolution. However, buck and ball worked as well or better in standard or even rifled muskets. Buck and ball loads were used by both sides of the American Civil War, often by cavalry units.