The range is 36'' to 240''
Between those two distances you can fire
directly or
indirectly. Direct fire requires line of sight, but the scatter is reduced by your ballistic skill. Indirect fire does not require line of sight.
If you're within your minimum range, though, you can only fire directly. You'll therefore require line of sight.
Note that it's still a Barrage weapon, regardless of whether you're firing directly or indirectly. You're still allocating wounds from the centre of the blast, hitting side armour, etc, etc. Also, you can't place the blast marker if it's touching a friendly. This includes the Basilisk, so you do have a minimum direct-fire range. It's two-and-a-half inches.
I seem to recall hearing you fire indirectly if under the minimum
I think it used to be that you could fire within the minimum, but only indirectly (i.e. you don't get the reduction in scatter from ballistic skill). 7th edition flipped it around.
EDIT: From the rules of Barrage weapons (I've got an online copy, so I can't quote page numbers):
If a Barrage weapon has line of sight to its target it can fire directly, even if the target is within its minimum range.