This is how I understand it: due to the nature of a SXS design each barrel forms a bending lever acting against the action. This lever causes each barrel to shoot to a different point than the unfired tube is pointed at. In other words, if there was no recoil the shot charge in each barrel would cross the line of aim a very short distance in front of the muzzle. However, the leverage resulting from the recoil moves the point of impact out much further--ideally to 40 yards. Clear as mud?

John McCain is my war hero.