T110's Northern Migration

The_Chieftain:   It's called parallax, and in modern tanks, it's accounted for by the ballistic computer. However, that's why we boresight at a known range 1,200-1,500m away, so that the system (and the backup sight) knows where the reference point is, as well as 1,200m being the battlesight range, which is the 'point-and-shoot' range without any ballistic computing necessary at all.   The location of the backup sight is, thus, also relevant. On the M1, and early Leopard 2s, it's down right next to the gun, so parallax is effectively non-existent. Leo 2A6s, though, have the backup sight mounted up on the roof, so it's more of an issue.   That said, I think the issue is over-stated. The parallax of 2 feet difference isn't likely to have much of an effect on if you're going to hit the target or not, except in the unlikely event that you're aiming for specific parts. More important is knowing if your gun tube is clear of obstructions.