That is an intersting link, but the fellar is rifle hunting. I read an article years ago that goes something like this: The path which a bullet travels is influenced downward or away from it's path by gravity. Gravity is most influencial in a perpendicular direction to the path of travel (####, I'm trying to explain this when "horizontal" isn't even clear). Therefore the bullet is least pulled away from it's path when shot an any angle upward or downward from horizontal. As you approach a straight up or straight down angle, then the bullet becomes less deflected from it's path (or line of bore). In fact in theory, if the bullet were to be shot either straight up or straight down (don't recommend you try this at home guys), it would NOT deviate from line of bore or path. After having said all of that, and the article I read dedicated three pages including diagrams and all, the final conclusion was that it wasn't significant enough for you to worry about....go figure. I wished I'd kept that article, because I have heard this question deliberated many times over.