See the post above for range modifiers.
The Thwipgun has a range of nearly 500 yards, but only does full damage out to 60. Aiming gets you +1 per second (up to +3, Acc-1 plus two extra seconds of Aim), All-Out Attack gives +1, getting into a braced position would be another +1, the centaurs are +1 because they’re big targets.
But their speed gives a -5, and a 100 yard shot is -10. And if they know you’re shooting at them, they can try to Dodge. So, what range do you want to let fly at?
