From Nikolas on Patreon:
"Have there been any attempts to make miniaturized man-portable chain guns? Do you think there's a future for such a machine gun given modern advances in energy storage?"

Chain guns are a specific type of externally-powered machine gun. They have a single barrel, and used a loop of chain to control the movement of the breech and feed system of a machine gun so that it cycles under external power independent of energy taken from the firing cartridge. They are most commonly used in:

- 20mm-30mm cannons
- Armored vehicle turrets
- Helicopters
- Naval AA mounts

The benefit of a chain gun is its ability to cycle a dud cartridge right through the system without causing a stoppage. They are also unaffected by variations in powder charge, within reason. This makes them idea for aerial mounts. The ability to lock the action closed longer than typical machine gun designs allows them to leak minimal propellent gasses out the breech, an advantage for use in tanks and APCs.

For infantry-type use, these benefits are not particularly useful. They are offset by the increased weight required of a chain gun, both from the additional components to actually the bolt and also the electric motor and battery to power it. I can see development of this system for autonomous or drone-based applications, but not for human infantry.