ARTILLERY MATERIAL. - SECTION 1.
Manual of Field Artillery Exercises, Canada, 1884
Designation.—Ordnance, wrought Iron rifled, M.L. 9 Pr. 8 cwt.
- nominal - 5 feet 8.5 inches.
- total - 6 feet.
- of bore - 5 feet 3.5 inches.
- of rifling - 4 feet 11.8 inches
- Preponderance - 7 lbs.
- Calibre - 3 inches.
- Nominal weight - 8 cwt. 1 qr. 6 lbs.
- Grooves - 3. French modified.
- Twist of rifling, uniform - 1 in 30 calibres.
- Initial Velocity - 1,381 feet.
Construction.—The 9 Pr. Muzzle-loading rifle gun consists of two pieces — one shrunk over the other; the "A tube" or "barrel," and the "breech coil."
The "A" tube," which extends the whole length of the gun is formed from a cylinder, or ingot, of cast-steel, bored and turned to the proper dimensions, after being toughened in a "bath" of oil.
The "breech coil" is of wrought iron, and is composed of two pieces welded together, the part in rear of the trunnions being manufactured from bar-iron, which is coiled round a mandrill and welded, the fibre of the iron running round in the direction of the length of the bar, whilst the part from close behind the trunnions to the front, is forged solid, this latter piece, after being rough-turned and bored, is welded to the coil.
The "breech coil" takes the form of a jacket to the barrel barrel, the two pieces having been turned and bored to the proper dimensions, the "breech coil" is expanded by heat, and then lowered over the "barrel " which is placed in a vertical position to receive it, the coil, on being allowed to cool, contracts so as to grip the barrel, the two pieces, in a measure, thus becoming one.
Sighting —The gun is sighted centrally with a tangent scale or hind sight, and a dispart or foresight.
The tangent scale consists of a rectangular steel bar, with head also of steel, the bar is graduated in degrees, each cross degree being subdivided into twenty divisions, a division being equal to three minutes of elevation. The cross head is grooved on the top, and is fitted with a gun metal leaf, which can be moved either to the right or to the left, to compensate tor accidental deflection, caused by wind, one wheel being higher than the other, etc., the front of the cross head is bevelled, and graduated right and left of the centre, in divisions reading three minutes each. The leaf is moved or clamped by means of a thumbscrew working in a slot in the back of the crosshead. The tangent scale works in a gun metal socket inserted in the breech of the gun at an angle of 1 deg. 30 mins. to the left, that being the angle which compensates for the derivation of the projectile, caused by the rifling. The cross head is fixed on the bar with a corresponding dip to the right so as to be horizontal when the scale is in use. When the tangent scale is lowered to zero its apex is flush with the upper surface of the gun this protects it from injury when not in use; when raised it is kept in position by a gun metal thumb screw.
The dispart sight is a small steel "leaf," screwed into the gun near the muzzle. The metal of the gun at this part is made the same thickness as at the breech, so as to form a dispart patch," and give a line parallel to the axis of the gun. This sight, also, is protected from injury in mounting, discounting, etc., by being fixed in a recess
Trunnions — The trunnions are 3.5 inches in length and diameter, and their axis coincident with that of the bore.
Vent — A hardened copper cone vent is screwed in so as to strike the curve at the bottom of the bore, both to ensure that the whole of the unconsumed portion of the cartridge may be blown out, and also for the purpose of firing very reduced charges. The highest initial velocity would be given by striking the cartridge at a point four-tenths of its length from the base, but the strain on the gun would be proportionately greater.