Advantages of multibarrel guns?

I find that they work rather well on railguns or coilguns which actually do tend to run dangerously hot, up to the point it slows down the firing rate. It makes it so I can also use thinner barrels so I don't have to radiate as much heat off, or if I really wanted to try some dumb stuff, like lining the barrels with rubber, for reasons.

Multibarrel works better with EM gun because the fire rate limiting factor of the EM gun wasn't loader mass, but power available to the gun system instead.

Want more fire rate? Pump more power.

Barrel started to overheat? More barrel!

Kinda wish the update came with other reload system for the conventional cannon so it can achieve even higher level of dakka...

I would assume that it is something akin to a rotary drum, like that of a later model thompson turned inside out, with a feed directly in the middle and some naval cannon style feed to work with the three degrees of movement of the turret itself. Considering you can stack the ammo storage, it's pertinent to assume it's got multiple decks, further complicating the loading and logistics.
It'd look a lot like the main cannons of a major naval battleship, except fully automated.
This complexity kind of makes me wish for an onboard malfunction submodule, or even the ability to walk around the storage bays (since quite a few of these guns would actually be big enough for active maintenance.)

I'd imagine you could get higher (and more energy efficient) loading speeds if you restricted the degrees of freedom and added a belt loader. A hull mounted turret with just pitch and a few degrees of yaw and a straight belt-loading mechanism. You could theoretically do a double belt loading mechanism for even more dakka.

On conventional guns that now start fully-loaded, you can use multibarreled guns as turreted, reloadable blast launchers. I've been tinkering with building cannons that shoot micromissiles with a high rate of fire in the hopes that guided weapons can offset the slow muzzle velocity and range of conventional guns.

For railguns and coilguns there reaches a point in high-velocity applications where barrel armor thickness, increased turret diameter, and other factors needed to offset overheating become so expensive or heavy that adding multiple barrels is a lighter, cheaper option. This especially applies to coilguns that have major heat buildup issues.

One thing that I would like in the future is the option to have a cooling jacket option for guns, similar to what older heavy machine guns had, it'd at least give the option to dissipate the heat from the barrel into a radiator.

On the loader question, I'm pretty sure we figured out that.

1. The ammo is supposed to be careless.
2. The actual loading mechanism is a linear induction motor, which is why more powerful loaders get heavier.
3. Loaders don't have an actual defined size, so technically you can fire black holes out of basically any gun if you use a 1 GW loader.