I was going to say what Ian Kirby said. Can’t point to a particular page but I remember there being a factor of 10 thing going on between personal and vehicular sized weapons. If you shoot a storm trooper with an x-wing they take 10 points for every point of damage that you inflict. Conversely, if you are a stormtrooper shooting at an x-wing then you can damage it but only if you do more than 10 points at a go. A Critical Hit could take out something important, though!