Weapons are sometimes linked to fire together in order to increase their chances of scoring a hit through the crude expedient of blasting more shots at the target. To represent the fusillade of fire laid down by a linked weapon you may re-roll the dice to hit if it misses. However if the second roll is also a miss you can't re-roll the dice again.
Linked Weapons
Source: Core Rulebook 3E, p. 58
Weapons fired together so that a missed to-hit roll may be re-rolled once.