@ZdrytchX The cartridges, yeah, thats right, but the other problems you mentioned are why it would make sense as a gatling gun. Its a fantasy, so we can assume its powered by "magic", making it that its several barrels rotating can get rid of the heat-problem/stress on the barrels, which should be the only problem if we assume that the necessary power is provided trough magic. So, it would be more like... several em-guns tied together?
I mean, we both know its just because its "cool" (personally i always thought gatling guns look rather stupid, but thats just me
) , but could be explained that way