Page:Aircraft in Warfare (1916).djvu/120

§ 49 162 grains of the Mannlicher, or the 530 grains of the old Enfield. The advantage of size and weight only becomes important when a single hit is sufficient to carry away an important strut or structural member which would have been penetrated without great injury by a bullet of ordinary size. Thus, so long as we are dealing with ordinary rifle, pistol, or machine-gun fire, we are concerned merely with the number of bullets that can be discharged per unit time, and this number—i.e., number per minute or second—fairly and properly expresses the value of the armament. This, of course, does not mean that the weight and muzzle energy of the bullets are of no importance whatever; it is merely an expression of the fact that with such weapons as are commonly available the differences, such as they are, and important though they may be in other applications, are not appreciable in relation to attack by aircraft on aircraft.

§ 50. Measure of Fire Value in the case of Explosive Projectiles. When we pass to the consideration of weapons capable of throwing explosive projectiles, it is impossible to maintain, or even suggest, any direct basis of comparison. The effectiveness of shell fire depends entirely upon the conditions being present necessary to the correct timing of the fuse—that is to say, either the range must be known with great accuracy and the time-fuse mechanism correspondingly perfect, or the nature of the target must be such as to permit of the effective employment of an impact fuse of some description. Granted that the necessary conditions exist, the destruction wrought by any given type of explosive projectile may be taken as, in a measure, proportional to its weight. However, there are cases when a 3 lb, high explosive shell would be just as effective as one of 18 1b., as, for example, if it were to strike the motor or fuselage of an aeroplane in flight, and so, in assessing the value of