What weapon did Leonardo da Vinci design with three rows of barrels?

Leonardo da Vinci designed a three-barrelled cannon as a rapid-firing artillery concept.

The design placed three cannon barrels together so that one set could fire while another was being loaded or repositioned. Leonardo’s aim was to improve battlefield efficiency without waiting for a single barrel to cool completely or be reloaded after every shot.

The concept belonged to a wider group of military-engineering studies made during Leonardo’s service to powerful Italian patrons. His notebooks contain ideas for artillery, fortifications, bridges, armored vehicles, and other devices. Many were exploratory drawings rather than construction plans prepared for immediate manufacture.

This weapon is often confused with Leonardo’s giant crossbow, which used stored elastic energy rather than gunpowder. It is also not the same as a modern machine gun. The three-barrel arrangement could support a faster sequence of shots, but it did not provide continuous automatic fire in the modern sense.