Danger Space
The span of distance over which the bullet's path stays within target height, so a hit remains likely despite range estimation error.
Danger space is the length of ground over which the trajectory stays low enough to strike a target of a given height without any change to the aim. As long as the bullet neither rises above the top of the target nor falls below its base, every range within that band produces a hit, which is exactly why it tolerates errors in distance estimation. The concept comes from military marksmanship, where a deep danger space against a man-sized target meant a single sight setting covered a wide swath of terrain.
The size of the danger space depends on the target’s height, the load’s flatness, and where the maximum ordinate falls along the path. It is closely tied to point-blank range, which defines the zero and aiming window that keep the bullet inside a chosen vertical limit. Understanding danger space helps a shooter judge how much a misread distance will hurt the hit at a given effective range.