As the title says. When locking the target in an MBT, the Fire Control System starts to automatically adjust range ("AUTO" is displayed on the weapons pane, where zeroing is) and lead.
However, it always underestimates range, resulting in the shell hitting around a degree lower than the target. This is not a problem with vehicles which are tall (Zamak/MRAPs); however, when engaging vehicles which have a low profile (tanks/APC), this causes the gun to miss - the round hits ground before the target.