gunpod
A gunpod is a detachable pod or pack containing machine guns or an automatic cannon, mounted externally on a vehicle. They are usually used in military aircraft.
Gunpods increase an air combat vehicle's firepower without occupying internal volume. When not required for a specific mission they can be omitted to save weight so the vehicle becomes lighter, faster and consumes less fuel.
Also used in some anime science fiction mecha series like MACROSS.