GUNNERY is the science and art of handling guns, the object being to inflict the maximum destructive effect upon the enemy in personnel, material and morale (i.e., troops and ship's crews; protective works, ships, guns, war materials and supplies; and mental condition as regards zeal, energy, hopeful and confident com bativeness, etc.). It consists of interior and exterior ballistics, gun strategy and tactics and the training of officers and men by means of instruction, drill and target practice. Interior ballistics are concerned with the developments within the bore of the gun; exterior ballistics, with the behavior of the projectile after it leaves the gun. Gun strategy defines what should be done to secure the best results. Gun tactics are the methods of carrying out OUR strategy. The scientific study of interior ballis tics has for its ultimate object the development of the highest practicable muzzle velocity in a gun which fires a projectile of the greatest prac ticable weight (for the calibre of gun) and largest practicable bursting charge. It Investi gates the problem of attaining these ends 'with out undue strain on the gun, without undue weight of gun, etc. Exterior ballistics follow the projectile from the muzzle of the gun to its point of rest or explosion, examining the veloc ity and trajectory of the projectile and the forces which produce changes in either. We thus endeavor to solve the problem of where and when a projectile of a given size, shape, weight and velocity of translation and rotation will strike under the action of the forces which effect its movement. Interior ballistics show that a high velocity requires high initial gas pressure in the gun and the maintenance of as high a pressure as practicable for the greatest practicable distance in the bore. The limita tions imposed by the present state of powder and gun development are, among others, an initial pressure of about 16 tons per square inch, a length of (heavy) gun of about 50 calibres, and a powder gas which is not unduly erosive. Higher pressures could be used, but with exist ing powders the increased amount of heat and erosion thereby produced would be inadmissible. Longer guns can be built; but after reaching 50 calibres the increase of accelerating force due to additional length is so small and the growth in weight (required to give necessary stiffness and accuracy) is so rapid that greater efficiency is obtained by employing the same weight in building a gun of larger calibre and less relative length. The present high velocities have been
rendered possible by the use of slow-burning powders which are not entirely turned into gas until after the projectile has moved some dis tance from its seat. The maximum pressure is thus kept down and the sustained pressure aug mented. In howitzers and mortars, velocity and range are sacrificed to obtain a large calibre extra-heavy projectile with a very light gun.
Were it not for the force of gravity • and the various effects of the air, a projectile would, upon leaving the muzzle of a gun, proceed with a uniform velocity in a straight line. In the let OZ be that line. The projectile reaches A in one second, B in two seconds, C in three and D in four, if OA—AB—BC—CD. If the projectile were fired in a vacuum where it was acted upon by the force of gravity but by no other disturbing forces, it would at the end of one second be at a instead of A, Aa being 16.08 feet, the distance an object will fall in one second under the influence of gravity. At the end of two seconds it would be at b, in three seconds at c and in four seconds at d. The curve Oabcd is a parabola with the axis verti cal. If the firing takes place in air in the ordi nary way the path of the projectile (i.e., its trajectory) will be still further modified. In stead of having a constant velocity and reach ing A, B, C, etc., the velocity is steadily de creasing so that at the end of one second (if gravity did not act) it would only reach some point A'; at the end of two seconds, B', etc. Gravity drops it to a b', etc., in which Aci==A'a'=B'b--B'b', etc. The curve Oa'b'c'hd' is the trajectory in air, the point d' being imag inary. The following table gives a comparison of the ranges in air and the theoretical ranges in a vacuum where the velocity of the projec tile, measured in a direction parallel to the axis of the gun, remains constant. The muzzle ve locity in all cases is 1,700 feet per second.
Striking Range velocity in air. III WWII°.