The charts for the 25pdr and 5.5inch guns are drawn for each charge (execpt charge 1). The principal and the methods of use are the same for all the charts.

For each charge there are two graphs of which the upper shows standard trajectories for given angles of departure plotted against angle of sight and range.

The range, under normal conditions is read in the lower graph vertically beneath any point on the trajectory, and on the horizontal line corresponding to the muzzle velocity of the the gun. The lower graph, which is virtually to reproduction of the range plate or range cone of the gun, shows the relationship, under normal conditions, between the angle of projection and range, for guns of varying muzzle velocity.