B5: Infinite range heavy beams ?

We played a game with the Earth Force Source Book space ship combat
rules 
last night, and the very first shot of the game caused a controversy.

>From 70 MUs away, a Narn assault cruiser fired a 2-dice heavy beam shot
at a 
Centauri Primus Cruiser.  As the rules are written, that meant each die
had 
a -11 on it, but if either rolled a 6, then that would be rerolled for
more 
damage with no modifiers.  Since assault cruisers recharge very quickly,

they could afford to take long, low probability shots like this.  Many
of 
the Centauri players thought this to be an exploitation of the rules,
and 
that the heavy beams should be limited to range 36 or 42 MUs, or that 
penalties above -6 should be applied to the rerolled die.

Have we misread the rules, or are we misjudging what we see as a
possible 
flaw in them ?

Tom
Tom + Dana McCarthy