Minecraft wiki entry for Arrow, associated text: There is a random variable to the trajectory of an arrow, given by this.rand.nextGaussian() * 0.0075 * (double)inaccuracy for the x, y and z coordinate. The inaccuracy is relatively small, becoming noticeable over larger distances. The inaccuracy of different arrow delivery devices may differ. Dispensers fire with an inaccuracy of 6, while bows fire with an inaccuracy of 1.