All weapons are capped at 0.1 rof. Turrets under AI control are capped at 0.25. Tools are 0.5. You can't set it faster than that. What you can do with the minigun is add another child and then when you right click you will fire double the rounds per second effectively making it 1200rpm. Note that you need to disable auto reload on the second child so that it doesn't eat all your ammo and that this method isn't normally supported so use at your own risk!
>cappred at 0.1 Terrible. Absolutely terrible. So to get actual minigun RoF (3000-6000) I'd need 5-10 children? Also, how do I disable automatic reload?