376 GUNMAKING 



and completely demoralised the crew. With this significant result before them, authori- 

 ties have not been slow to recognise that the bursting of very few large high explosive 

 shell behind the armour might speedily decide an engagement. 



Supposing for the moment that the calibre of the gun was approximately equal to 

 the thickness of the plate, it is evident that as the quality of the armour improved the 

 perforating energy of the projectile had to be increased, and, as the fighting range be- 

 came more distant, a higher initial velocity was required. Both these conditions operate 

 in the same direction, i.e. in an increase in the muzzle velocity of the gun. Moreover, 

 some authorities were manifestly reluctant to increase the calibre on account of ques- 

 tions of interchangeability, and the additional weight to be accommodated. 



For these reasons, the muzzle velocity of heavy guns up to and including 12 inches 

 diameter has had to be considerably increased by (a) making the gun longer, (b) in- 

 creasing the weight of the charge; and as it is generally admitted that the length of the 

 gun bore should not exceed 5o-calibres, but should be shorter if possible owing to the 

 tendency to vibration and a consequent loss of accuracy of long guns on firing, the gun 

 maker has to face an augmentation in the weight of the charge. This, however, he 

 endeavours to keep as small as possible, by increasing the chamber pressure and making 

 the gun and projectile stronger to withstand it. 



The addition to the weight of the charge, to the chamber pressure, and to the length 

 of the gun, all tend to increase erosion and to shorten the life of the gun. Speaking 

 broadly, the erosion of equally proportioned guns is, for similar velocities, dependent on 

 some function of the calibre, and the high velocities until recently demanded may be 

 regarded as responsible for the comparatively short life of the guns designed to produce 

 these velocities. Naturally, the life of the gun, i.e. the number of full rounds it is 

 capable of firing before it is worn out, has a most important bearing on its efficiency, 

 especially at the present time when many rounds are fired annually for exercise purposes. 



It has therefore been necessary to consider some means of increasing the life of the 

 gun, of ensuring perforation of improved armour at fighting ranges of 8,000 yards, and 

 of bursting behind that armour a high explosive shell containing a powerful bursting 

 charge. These conditions were met in the British Navy by the introduction in 1910 of 

 the 13. 5-inch gun. This gun, with a moderate velocity, has, owing to its heavy pro- 

 jectile, a considerable surplus of perforating energy over that of the high velocity 12- 

 inch gun at the fighting range of 8,000 yards, and this surplus increases with the range. 

 The 1 3. 5-inch gun with its comparatively low velocity requires a charge no larger than 

 that of the 1 2-inch gun, and in consequence this gun can fire from i\ to 3 times the num- 

 ber of rounds that the 1 2-inch gun is capable of firing. As first designed, the weight of 

 the projectile was exactly the same as that for the 13. 5-inch B.L. gun of 1885, viz. 1,250 

 Ibs. ; recently, however, a tendency to increase the relative weight of the projectile has 

 set in, on account of the larger bursting charge which they may be made to contain, and 

 in accordance with this the projectile has been increased in weight to 1,400 Ibs. 



Formerly, it was supposed that the length of projectile which could be relied on to 

 give accurate results was limited to about 4 calibres, and that any increase in its weight 

 simply implied thicker walls and a smaller bursting charge; but recent experiments with 

 heavy guns give accurate results with projectiles up to 5.5 calibres in length. One argu- 

 ment against a relatively high weight of projectile therefore vanishes. 



It is not to be supposed that the calibre of the gun will be limited to 13.5 inches. 

 Germany and the United States are already manufacturing i4-inch guns, and the Japa- 

 nese (iovernment, besides constructing guns of this calibre, are also acquiring in England 

 a number of similar guns. Other nations are following this powerful lead, and signs 

 have not been wanting of further developments. 



Gun power has also been increased by improvements in the shape of the head of the 

 projectile. Until two or three years ago, the radius of the ogive had been 2 calibres, but 

 experiments with pointed bullets having a radius of head of from 6 to 8 calibres had 

 shown that the sharper form of head gave, owing to the reduced air resistance, higher 

 remaining velocities at all ranges; and consequently for any given range a much flatter 



