Object 
rifling 
guns. 
26 
PRINCIPLES OP GUNNERY. 
RIFLED ORDNANCE. 
BY 
CAPTAIN J. SLADEN, E.A. 
(Professor of Artillery, B.M. Academy, Woolwich). 
CHAPTER I. 
Teems used in Gunnery. 
Object of Rifling Guns.—Projectile centred.—Line of Eire.—Trajectory.—The Plane of Fire.—Line 
of Sight.—Angle of Elevation.—Angle of Departure.—Jump.—Angle of Fire.—Angle of 
Descent.—Range.—Terms distinguishing the various Natures of Artillery Fire.—Direct Fire.— 
Indirect or Curved Fire.—High-Angle Fire.—Front Fire.—Oblique Fire.—Enfilade Fire.— 
Reverse Fire.—Deflection.—Muzzle Velocity.—Resistance of the Air.—Remaining Velocity.— 
Retardation.—Striking Velocity.—Horizontal Velocity.—Vertical Velocity.—Gravity.—Ter¬ 
minal Velocity—Calibre.—Windage.—Clearance.—Disadvantages of Windage. 
With smooth-bore guns, a frequent cause of inaccuracy at mo¬ 
derate ranges is due to the uncertain rotation communicated to the 
projectile in the bore of the gun; so that it never can be confidently 
predicted whether the projectile will deflect to the right or left. With 
rifled guns, on the contrary, rotation is impressed on the projectile 
by means of spiral grooves cut in the gun; so that the rotation is 
no longer uncertain, but always takes place in a fixed direction, giving 
a constant deflection, which can be allowed for in laying the gun. 
Moreover, it becomes possible, by giving sufficient rotation to an 
elongated projectile, to keep it point first during its flight through the 
air j and so to diminish the effects of the resistance of the air,* by 
increasing the ratio of the weight of the projectile to the diameter of 
the bore, and also by giving the head of the projectile any desired 
shape. Hence arises greater accuracy, greater effect of shell, greater 
penetration, and a flatter trajectory. 
* See pamphlet by the author, “The Merits of a Large Bore and Small Bore Contrasted.” 
{“'Proceedings, R.A. Institution,” Vol. VII. p. 273.) 
