Quick point of interest regarding the minigun and other rotary, multi-barrelled weapons: There is no lag time to spinning up the barrels. That is entirely a game balance conceit from video games. In reality, once the firing trigger is depressed, the weapon is firing. Each barrel is in various states of loading and unloading, with one barrel containing a live round with the mechanism ready to fire.
I've removed the so called "spin up time" from my games, because it is completely silly. No one would engineer a weapon that way, in the first place, and IRL no one has.