They're based on knowing exact average damages, exact chances of any crit result and knowing that the majority of players talk totally out of their arses when it comes to combat balance. The difference between big and small guns is reasonably small. This is why all past changes to the top end weapons have been small and will continue to be.
@Reginmund I never assumed that would be the only change, I asked if there were any other changes planned for them when the duration update is done, I got no answer so that is the only thing i can comment on.
