I always thought some guns had electrical power.
Gun reloading requires energy and this can be achieved essentially in two ways: storing the energy accumulated during the combustion of the cartridge or by an external source. Some guns in GOIO (involving bullets and discharge gases)
could automatically reload by storing the excess energy produced in the event of firing but for others (rockets mostly) it is simply impossible hence
an external energy source is necessary.
the second argument in favor of electrically powered guns is
tilting.
Lumberjack easily weights an excess of 4 metric tons, ignoring the automatic feeding mechanism and ammo storage. Same goes for any other heavy gun. In order to tilt it with such precision and speed an external power source other that muscle is required. the gunner sits on a chair, not actively participating in tilting other that providing an analogical input which is then transferred to servomotors that provide 2-axis movement. While this could be achieved through a chemical engine and steam pistons, none is to be seen on the actual gun. Instead a
rotary servo motor is visible at the base of the gun and on the vertical joint, provinding the aforementioned two axis tilt.
A linear actuator control box is seen between the two, right next to the gunner's position with reinforced cables jutting out.