This trajectory is meant to echo those shown in British musketry manuals (see below) of the period to show the “danger zone” of a particular weapon. The danger zone is the area from “first catch” to “first graze” at any particular sight setting. First catch is the range at which a bullet fired at that given sight setting will hit a standing man at the top of his head, and first graze is the range at which that same bullet would hit a man on his foot. Thus, the danger zone is the range over which a given bullet would hit an enemy somewhere from the top of his head to his foot when you aim at center mass. At normal rifle ranges, the trajectory will pass over an average soldier’s head for quite some distance, so knowing the danger zone is quite important. With black-powder rifles danger zones start very wide, but at very long ranges the zone shrinks dramatically because of the parabolic nature of the bullet trajectories.
Note that the trajectory chart starts at 56 inches off the ground because that is the height of an average man’s shoulder.
Working from the assumption that the maximum effective range of the Smith Carbine is 150 yards, we can see from the above that the danger zone is the entire distance at which the weapon can be fired since first graze is at approximately 195 yards. Thus, using this load and this bullet, if you aim at center mass you will it an enemy somewhere on his body at any normal shooting range for the weapon.
Note, however, that this information is based upon the load I use (i.e., 35 grains of 3F Schuetzen black powder with a 360-grain Eras Gone bullet) fired from my reproduction Pietta carbine. For detailed information about how I load cartridges for my Smith carbine, go here. Given that the original Smith load was closer to 50 grains and that nineteenth-century power was, in general, of much higher quality than we get today, and given that I cannot compare the rifling of the Pietta with an original, it is almost certain that these results do not match what an original would have. Regardless, this information is useful for me as a way of estimating how to aim off for distance with my carbine. For example, looking at the graph I can see that the highest point of the trajectory is 59.27 inches from 40 to 50 yards, whereas it is 54.04 inches at 100 yards, so I can see that I must aim about six inches lower when shooting at that distance than I would if I were shooting at 100 yards, and that matches well to my empirical experience.
