472 



GUNPOWDER 



moulds is then pressed by plungers exactly fitting 

 the moulds till the required density is obtained. 

 This powder is called prismatic powder, the grains 

 or pellets being in the form of hexagonal prisms 

 nearly 1 inch in height and about 1J inch across, 

 with a hole in the middle about ^tli of an 

 inch in diameter, the object of which will be 

 explained later on. There are two descriptions of 

 prismatic powder black and brown. The propor- 

 tions of ingredients in the black powder are the 

 same as in all other English military powders ; but 

 in the brown powder the charcoal is made from 

 straw, instead of from wood, and the proportion of 

 the ingredients are as follows : viz. saltpetre 79, 

 charcoal 18, and sulphur 3 per cent. 



Gunpowder more nearly fulfils the objects 

 required in a propelling agent than any other 

 explosive hitherto discovered. These objects are 

 ( 1 ) a maximum muzzle velocity with even and low 

 pressures; (2) uniformity of action, so that the 

 same results may always be expected ; (3) freedom 

 from fouling; (4) durability i.e. that it is not 

 liable to injury in transport, and that its condition 

 does not materially alter when stored. 



The advantages of gunpowder over other explo- 

 sives are ( 1 ) that, the rate of combustion being 

 gradual, the explosion is not so severe on the bore 

 of the gun as in the case of more violent explo- 

 sives ; (2) the ingredients of which it is composed 

 are easily produced and are cheap ; (3) it is, with 

 proper precautions, safe in manufacture, in store, or 

 in transport. Experiments made by the Explosives 

 Committee have shown that any altercation in the 

 proportions of the ingredients has not so great an 

 influence on the ' explosiveness ' or rate of burning 

 as the density, hardness, size, and shape of grain 

 and amount of glaze. The density of grain has an 

 important effect on the rate of burning. By 

 absolute density is meant the amount of powder 

 actually present in a certain bulk i.e. if different 

 quantities of meal-powder, containing an equal 

 amount of moisture, be pressed into cakes of the 

 same size, that which contains the most meal 

 will be densest ; then, if these cakes be ignited 

 simultaneously, the cake which has the least 

 density will be the first to be completely burnt. 

 Hardness does not depend on density ; increased 

 hardness is given by pressing the meal in a moister 

 condition. Size and shape of grain are also import- 

 ant characteristics to be considered in connection 

 with the explosiveness of powder. Other things 

 being equal, a larger-grained powder burns slower 

 than a smaller-grained ; and in grain of equal 

 weight that which has the largest surface will burn 

 the quickest. A highly-glazed powder, again, 

 burns slower than an unglazed one, probably be- 

 cause the glaze somewhat retards its thorough igni- 

 tion. The temperature at which powder ignites 

 varies from 530 to 600 F. , according to the nature 

 of the powder, the finest sporting powder igniting 

 at the higher temperature. 



It is only of Lite years that all these points have 

 received the attention they deserve, but they have 

 been forced upon the authorities by the necessities 

 of the times. As soon as ships began to be plated 

 with armour, guns had to be made which could 

 throw a projectile capable of piercing that armour ; 

 and as the armour increased in thickness so did the 

 guns increase in size and power, throwing heavier 

 projectiles, which necessitates an enormous powder 

 charge to propel the shot. In former days there 

 was a beautiful simplicity about powder. Practi- 

 cally there were but two kinds, one for muskets 

 called fine grain or F. G. , and the other for cannon 

 called large grain or L.G., and no particular atten- 

 tion was paid to the quality ; it was certainly not 

 subjected to the searching proofs and tests which 

 all powders made in these days have to undergo. 



The first improvement in powder took place on the 

 introduction of rifled arms, when a rifle fine-grain 

 powder or R. F. G. , slightly larger in the grain than 

 F.G., and a rifle large-grain powder or R.L.G., the 

 grains of which were about twice the size of those 

 of L.G., were introduced for small-arms and cannon 

 respectively. The R.F.G. powder was improved 

 and made of a rather smaller grain, the size of 

 grain being from T \th to -^Vth of an inch, on the 

 introduction of the Martini-Henry rifle, and this 

 powder; known as R.F.G. 2 , has not since been 

 altered. But in cannon powder, or powder for 

 large guns, the development has been great and 

 continuous. When R.L.G. powder was introduced 

 it was the largest grained and slowest burning 

 powder then in existence in England ; but as the 

 guns were made larger and larger it became 

 necessary to use a slower-burning powder, which 

 led first to the introduction of R.L.G. 2 , having 

 grains varying in size from 3 to 6 to the inch ; that 

 is, the grains must pass through a sieve of 3 meshes 

 to the inch, and must not pass through one of 6 

 meshes to the inch. A short time afterwards a still 

 larger powder called R.L.G. 4 , with grains of nearly 

 half an inch in size, was introduced. This was 

 soon followed by pebble powder, a still further 

 development of R.L.G., for guns of large calibre 

 for which R.L.G. 4 was not suitable. The first 

 pattern of pebble or P. powder was cut in cubes of 

 about half an inch in size, and a second pattern or 

 P. 2 was made in cubes of about 1 inch in size, 

 with rounded edges. Both these powders have a 

 density of T75, whereas that of theR.L.G. powders 

 is 1 '65. Next in order came the prismatic powders, 

 of which there are two descriptions viz. prismatic 

 black or Prism 1 and prismatic brown or Prism 1 

 brown, a description of which has been given under 

 the head of manufacture. There are two other 

 powders of a special pattern which may be men- 

 tioned viz. M.G. 1 which is used only in the 1-inch 

 Nordenfelt machine gun, the size of grain of which 

 is considerably larger and of more even size than 

 that of R.F.G. 2 ; and Q.F. 1 , a powder which at 

 present is used only in the 3- and 6-pounder quick- 

 firing guns, the size of grains being about half an 

 inch square by about T V of an inch thick. 



The powders of other nations differ but slightly 

 from those manufactured in England ; the method 

 of manufacture is the same in principle, but the 

 proportions of the ingredients vary to a slight 

 degree in every nation. 



Having now described the various powders in 

 use, it remains to say a few words about velocities 

 and pressures. The great desideratum with all 

 firearms is to obtain the maximum velocity with 

 the minimum of pressure, and in the experiments 

 and investigations carried out by the committee on 

 explosives, and by Sir F. Abel and Sir A. Noble, 

 this end was kept in view. It has already been 

 pointed out that the rate at which powder burns 

 depends greatly on the density, hardness, size, and 

 shape of grain : the greater the density the slower 

 it will burn ; the larger the grain the slower it will 

 burn, simply because the amount of lighting sur- 

 face is reduced in proportion to the volume ; and 

 the smoother the surface of the grain the slower it 

 will burn for the same reason. A powder there- 

 fore composed of, comparatively speaking, small 

 grains of irregular size and shape, burns very 

 rapidly, and generates a large volume of gas sud- 

 denly, thus setting up a very high pressure in the 

 bore of the gun. In some of the experiments of the 

 committee the pressure recorded in the bore of the 

 gun was as high as 60 tons to the square inch ; but, 

 as Captain Noble had previously discovered that 

 the maximum pressure of powder fired in a con- 

 fined space did not exceed 42 tons, this extra pres- 

 sure could only be due to wave-action, a sudden 



