Chaos ships do better at close range than they do at long range. This is axiomatic. However, they do not necessarily do better than other races ships at close range, whereas they usually do better than other races ships at long range. Therefore in closing the range with a Chaos fleet you tend to pass the advantage to the opponent.
Of course, your opponent will be attempting to close the gap and so it will eventually pass to him. The damage you do at long range is meant to offset this advantage to a degree. Your choice of target, efficacy of shooting and manoeuvring will determine the outcome of this advantage shift.
For example, try to avoid letting the enemy split your line with gunships on LO with closing/away ships on each side at close range. You will lose. Also, do not waste long range gunnery on battleships. Basically, don't shoot at a BB unless you can predict at least crippling it if the opponent doesn't brace. Anything less and you're generally just wasting your firepower. If you have a choice between shooting at a closing Lunar or a closing Dauntless with your WBs, choose the latter. Very easy VPs and you get rid of a good deal of firepower on a fast and agile platform.
Lastly, be ready to pounce. Sure you may generally want to stay at range, but remember, your ships do better up close than they do from afar. So if you can power forward and get in a killing blow then this can often reduce the return fire drastically enough to mitigate any advantage your opponent would normally gain.
