344 
MINUTES OF PROCEEDINGS OF 
The grooves make 0*53 of a turn from left to right in the length of the 
bore rifled. The pitch angle is 8J°.* 
In order to comprehend the principle upon which the grooving is con¬ 
structed, it is necessary here to describe the exterior form of the projectile, 
and to show the position of the projectile in loading and firing. 
The cylinder of the projectile is similar in section to the bore, having 
six wings or ridges exterior to the generating cylinder. Pig. 3 shews the 
outline of the projectile in section, the generating circle being shewn by 
the dotted line, and the outlines of the ridges by the full lines. The form 
of the ridges corresponds to that of the grooves, but the diameter of the 
generating circle of the projectile is 0 ,/# 065 less than that of the bore. 
Supposing the projectile entered into the bore in the act of loading (Fig. 4), 
the lower ridge l would lie at the bottom of the lower groove, whilst 
between all the other ridges and their corresponding grooves, there would be 
the windage shewn in the drawing; at the point h it amounts to 0"‘065, 
the difference between the diameters of the bore and projectile. In this 
position the projectile is rammed home in loading up to the smooth-bored 
powder chamber; in going home it makes the amount of revolution 
determined by the twist of the grooves, and slides with the lowest ridge 
constantly in contact with the bottom of the corresponding groove, in 
virtue of its weight. As soon as the bottom of the projectile has reached 
the rear end of the rifled part of the bore, the projectile is twisted to the 
right by the rammer head which is specially adapted to this purpose, and 
thus is brought into the position shewn in Fig. 5 ; in this position the 
ridges of the projectile are in contact with the parts Im of the arcs of the 
grooves, whilst the windage is distributed in the manner shewn by Fig. 6. 
In this centred position the projectile is driven forwards by the impulse 
of the pow'der gas, and is at the same time set in rotation from left to 
right by the twist of the grooves. The right sides of the grooves, as seen 
from the front of the gun, form the bearing surfaces for the ridges; they 
guide the projectile, and keep the long axis of the projectile, while in 
motion, in the axis of the piece. 
This construction of grooving admits of sufficient windage for easy 
loading, while at the same time the projectile is supported in its centred 
position in firing; and as the bearing surfaces are proportionately large, 
the projectile has a much steadier motion on this system than on any 
other system in use with muzzle-loading guns. 
The system of sighting (Fig. 7) is as follows:— 
At the upper surface of the breech is a flat p with a short v shaped 
engraved line i ; the former forms a footing for the base of the tangent 
scale in firing at short distances, the latter is used for line-of-metal 
sighting; on the rear surface of the base of the breech on the right-hand 
side is a groove, into which the base of the tangent scale fits in firing at 
long distances. On the shoulder of the right trunnion is a steel centre 
sight with V notch, attached by tw r o screws; the sighting is taken over the 
centre sight when the tangent scale is entered into the afore-mentioned 
groove on the breech-base. The muzzle has a dispart patch with V notch. 
The line of sight with an elevation of 0° is parallel to the axis. 
* One turn in 24'13 calibres, 
