If order of your rules is important, why is #5 after #4?
Because of simple mechanics. It is harder to make the second follow up shot than the first. Thus the second shot has a much higher chance of missing. See rule #2. Rule #5 addresses the capacity issue.
Banging a whole lot of rounds down range is not as critical as actually hitting the target. Thus the capacity of rounds of a particular firearm takes a back seat to hitting the target accurately and putting a big enough hole in the person that they stop fighting.