No other weapon has changed the face of the battlefield as the machine gun. It's design and and association with mass death makes it a great and powerful weapon. Two men, Hiram Maxim and Richard Gatling, made huge impacts in the development of the machine gun, making it a useful form of artillery for the military. Maxim and Gatling designed capable and reliable versions of machine guns in a time when others were producing clunky, unreliable models.
Volley Guns (Chivers, 2010, p.26), also known as Organ Guns (Ellis, 1975, p.10) were first attempts at increasing firepower by adding several barrels to the firing itself, rather than simply attempting to increase the rate of fire. "Gunsmiths had long ago learned to place barrels side by side on frames to create firearms capable of discharging projectiles in rapid succession. These unwieldy devices, or volley guns, were capable in theory of blasting a hole in a line of advancing soldiers"(Chivers, 2010, p.26). An example of this type of weapon was noted in 1835, when "Giuseppe Fieshi unleashed terror on King Louis-Phillipe in Paris, France, firing a 25 barrel volley gun", killing 18 of the king's entourage and grazing the King's skull. The weapon was ineffective however. Four of the barrels failed and another four ruptured. Two other barrels had exploded inside, grievously wounding Giuseppe"(Chivers, 2010, p. 27). .
These weapons were impractical for military use, but attracted many people to the arms race for weapons that could sweep the battlefield. "They had limitations in practice, among them slow reload times and difficulties in adjusting fire toward moving targets and their flanks. Ammunition was a problem, too, as was the poor state of metallurgy, although this did not discourage everyone, and the lethal possibilities of a machine that could concentrate gunfire attracted would-be inventors of many stripes" (Chivers, 2010, p. 26-27); and indeed this did.