The max range is the lower of the weapon range or the fire control range. For weapons like the laser that can far outrange the fire control the benifit you get is doing more than 1 point of damage at that max range. For example if my laser does 64 points of damage at min range, and has a max range of 20m km then at 1m km I will still be doing 60 points of damage, which will penetrate a lot of armour. This is the only benifit of using weapons with ranges significantly greater than your fire control range. The numbers I used above are somewhat arbitrary but the math is correct and should give you an idea of what is going on.
Brian