The Ballistics of the Snider-Enfield Rifle

Remarks:
The calculated height for cavalry forces is 8 1/2 feet, that for the infantry is 6 feet.
The rifle is 4 1/2 feet above the ground at distances to 300 yards; beyond that distance, 3 feet above the ground (this is because at ranges up to 300 yards the soldiers are taught to fire standing, while at ranges beyond that they are taught to fire from the kneeling position).
The object hit 3 feet above the ground at each distance.
N.B. The first catch and first graze are given in divisions of 5 yards to assist the memory, hence are only approximations.

15. It will be seen from the above table that if the Snider-Enfield rifle be fired from the shoulder, standing, at the centre of a bull's eye 3 feet from the ground, with the elevation for 100 yards, its axis must be directed at a point 3 feet 10 inches from the bottom of the target, and the height of the firer's shoulder being taken at 4 1/2 feet, the bullet in its course does not anywhere rise above the latter height. It will also be observed that the bullet which, in this distance falls only 10 inches, would, after passing through the centre of the bull's eye (if the target were made of cotton or paper) strike the ground at 80 yards beyond it,-showing that in that distance it falls the height of 3 feet,-and consequently, in passing over the second hundred yards, it would from the continually increasing curve fall more than 4 feet, thus proving what was shown in the second lesson, that the elevation for 100 yards would not be sufficient for 200 yards, or any greater distance.

—Regulations for Conducting the Musketry Instruction of the Army. 1870. pp. 35-36.

The specific Mark of cartridge is not specified in the above manual but can be assumed to be a 480-grain bullet (with plug) over 68-72 grains of RFG ("rifle fine grain") powder since the document dates from 1870 (the bullet weight dropped from 525 grains in Marks I-II to 480 grains in later marks from 1867 onward).

"The Snider bullet weighs 480 grs. : the powder charge 70 grs. of R. F. G. : wt. of a bundle of 10 cartridges about 16 oz." (General Viscount Wolseley.  The Soldier's Pocket Book for Field Service. London: Macmillan and Co. 1886. p. 109.)

Definitions:
Distance is the setting on the rifle's rear sight.
First Catch is the first distance at which a round will hit either a cavalry or infantry soldier in the head at that sight setting.
First Graze is the distance at which a round will hit a soldier's feet at that sight setting.
Margin is the distance between "First Catch" and "First Graze" at that sight setting.  In other words, this is the range over which a bullet will strike some point on an enemy (from his head to his feet) for any given sight setting.
Point Blank is the point at which the bullet's trajectory crosses the line of sight for any given sight setting; also known as "far zero" today.*

Decreasing Margin:
Note that the chart above makes it plain that the margin decreases in width as the range setting increases.  Thus, at the 300 yard setting, the margin--i.e., the distance between first catch and first graze--is 135 yards for infantry, but that the margin decreases to only 30 yards at the 600 yard setting.  This is because the bullet trajectory is a parabolic curve which drops off much faster toward the end of its flight than it does at the beginning as the force of the shot decreases over time and the effects of gravity and wind resistance assert themselves more strongly.

Figure 9:  The Line of Fire; Bullet Trajectory; and Line of Sight (top to bottom).
Figure 10:  First Catch and First Graze versus infantry with the sight set at 300 yards.
Figure 11:  First Catch and First Graze against cavalry and infantry with the sight set at 600 yards.
From:  Regulations for Conducting Musketry Instruction, 1870, p. 165.  The cleaned-up rendering of the above drawing is courtesy of Grant Rombough.

Snider Ballistics:
Bullet weight:  480 grains (including plug).
Barrel length:  36 inches.
Sight Radius:  31.6 inches.
Powder charge:  68-72 grains of "R.F.G." or "Rifle, Fine Grain" which is similar to modern Swiss 1.5F.
Muzzle velocity:  1,250 f.p.s.
Muzzle energy:  1,666 ft. lbs.
(These figures assume a Mark III et. seq. cartridge.)

*Although some ballistics texts seem to use a slightly different definition of "point blank," the definition used here is that to be found in shooting manuals of the Nineteenth Century.  For example: "[P]oint-blank (V) is the second intersection of the trajectory (T K), or curve, with the line of sight." (Heth, Henry.  A System of Target Practice for the use of Troops. New York: D. Van Nostrand, 1862. p. 17.)