The following is not official, but is a pretty solid reflection of how Factory Judges and canon approach starship gun/sensor ranges.
SHORT: Starfighter weapons. Capital ship defensive weapons.
STANDARD: Normal capital ship weapons - turbolasers, etc.
LONG: Special weapons - long-range turbolasers are the main example.
EXTREME: Special weapons - energy torpedos and hypervelocity guns are the main examples.
You can also use these ranges for sensors (a starfighter might have Short range; a command ship might have Long range; a dedicated sensor ship might have Extreme range) or for interdiction (your average gravity well projector will have an effect out to Long or Extreme range; pulse-mass/gravity mines, or some of the similarly sized probes I've made could be said to have Short range).
It's important to note that canon varies immensely as to what numbers to assign to each of these proportional slots. Some sources say a turbolaser's range is 50-75 km; others say it's orders of magnitude longer. That is a MUCH larger debate, and some people get really strong feelings about it for no reason.
As a result, I definitely recommend NOT using numbers to define weapon ranges, as numbers will mean something radically different to any given writer's understanding of the above, and what canon sources they're using. Instead, I suggest saying something like 'Range: Standard (comparable to a turbolaser).' That's a tried-and-true method of making sure that your weapon sub does what you actually think it does. In fact, the Short/Standard/Long/Extreme system is how both judges and some newer canon materials (the FFG RPGs for one) sidestep the entire numbers issue.
As a side note, if you enjoy writing starship/fleet battles, get to know Short/Standard/Long/Extreme intimately. Virtually every experienced fleet combat writer on the board uses it or something like it. It's a great way to avoid misunderstandings and prevent handwaving.