Nitrox: "I'm guessing the open sights haven't crossed yet at 50 yards. What do they do after 50 yards and before 100 yards? Have they crossed by then?"

A properly well regulated double rifle's bullets will never cross, but will shoot parallel to infinity, within reasonable range for caliber. Some guys are under the misconception that a double rifle should cross, usually at range rifle was regulated for--50 yards, 75 yards, whatever, but that is simply not true.