Systems for shooting down flying objects have been using multiple barrels forever.
In WWII, a lot of weapons used two or four barrels, such as the British pompom guns, or the 40-mm Bofors. The Iowa class battleships had 20 quad mount Bofors systems for a total of 80 barrels.
Fighters also had multiple machine guns that fired together. The P-51 had six 50 cal machine guns firing together.