Leonardo da Vinci arranged 33 gun barrels in his famous multi-barrel cannon design.
The weapon is commonly called the organ gun because its parallel barrels resemble the pipes of a musical instrument. Leonardo arranged the barrels in three rows of eleven. The design was intended to fire a concentrated volley and then allow a different row to be loaded while the others cooled.
This arrangement addressed a major problem with early gunpowder weapons: slow reloading. A single cannon could fire only occasionally, while a group of smaller barrels could produce a rapid sequence of shots. The design still depended on contemporary gunpowder technology and would have been heavy and difficult to move.
Leonardo’s multi-barrel weapon was a proposal, not a battlefield innovation known to have been built and used by him. Similar volley guns appeared in other historical contexts, so the design should not be treated as the sole origin of all multi-barrel firearms.