When a battery unlimbers near another battery already in action and opens fire upon the same target, it should obtain the range from the latter.
The duty of finding the range generally devolves upon the captain of each battery, even when several batteries open fire upon the same target. Whenever several batteries open simultaneously to find the range of a target of limited dimensions, the fire of each battery must be concentrated upon an entirely distinct point, and all of the points must be far enough apart to enable each battery commander to distinguish the fall of his own projectiles from those of the neighboring battery.
It is only in very exceptional circumstances that the battalion commander would take personal charge of the firing of his battalion in order to establish the range himself.
Trial Shots.—A percussion-shell is fired with the elevation corresponding to the estimated range at a clearly visible and sharply defined fixed point of the target.
If the first shot strikes short, or beyond the target, the range for the second is either increased or decreased, according to the case, so as to throw the shot beyond or short of the target.
These corrections are generally made as follows:
| When firing at short ranges, | 100 | yards. |
| When firing at medium ranges, | 200 | " |
| When firing at long ranges, | 400 | " |
Such firing is pursued until two consecutive shots fall, one short of and the other beyond the target, which establishes "the long bracket, or fork."
No round should be taken as a basis for correction if there is any doubt as to the reliability of the observations.