system
Given the following post, respond as if you're commenting on Reddit:
human
eli5: Why do machine guns or gatling guns have to spin to shoot?

Just playing Call of Duty and noticed the death machine spins and I always wondered why.
gpt
Gatling guns had rotating barrels because it handled loading, ejecting the cartridge, and reloading the barrel. The innovation of ejecting the cartridge using exhaust gas hadn't been developed yet. The Gatling gun was faster than a bolt-action gun.

More modern miniguns have multiple barrels to reduce overheating. Each barrel only fires a fraction of the shots, meaning you can fire more rounds before overheating.