Objects 
sought 
after by 
the use of 
powder as; 
propelliug 
agent. 
Causes 
which 
affect the 
time of 
explosion 
of powder. 
48 PRINCIPLES OP GUNNERY. 
Table showing the Results of Explosion of P. and R.L.G. Powder. 
Charge of 
powder. 
Weight 
of projectile. 
Muzzle 
velocity. 
Maximum 
pressure in 
the chamber. 
Time of 
max. press. 
Distance traversed | 
in that time by 
projectile. 
lbs. 
f.s. 
tons per sq.in. 
sec. 
ins. 
70 lbs. P. 
300 
1527' 
18 
•00437 
6-0 
60lbs. R.L.G. 
300 
1480 
22 
•00070 
•6 
The force developed, then, by fired E.L.G. powder approximates 
more to the nature of an impulse than that developed by fired 
P. powder, and consequently exerts a more destructive strain on both 
gun and projectile’. It is for this reason that P. powder has been 
substituted for E.L.G. powder in the charges of the heavy rifled 
M.L. guns. 
The chief object to be attained by the use of powder as an explosive 
agent in the bore of a gun is to transmit the greatest amount of muzzle 
i energy to the projectile with the least possible strain to the gun— i.e., 
to transmit the maximum of total pressure to the base of the projectile, 
throughout the bore of the gun, with the minimum of local pressure to 
the powder-chamber. 
The time of explosion of powder depends principally on the size and 
shape of the grains, their density and hardness, the amount of glazing’ 
given to them, and the quantity of moisture contained in the powder. 
Suppose a powder similar in all respects except in the size and shape 
of the grains; then the time of explosion, or conversion of the powder 
into gas, depends on the rate of ignition of the grains, and the time of 
combustion of each grain. 
The rate of ignition of the grains depends on the facility with which 
the flame can penetrate to contiguous grains— i.e., on the magnitude of 
the interstices between the grains, depending principally on the shape 
of the grains; while the time of combustion depends on the bulk or size 
of the grains themselves— i.e., the smaller the size the quicker the 
combustion. These conditions (more fully explained in a treatise on 
gunpowder),* are to a certain extent opposed to one another; so that 
it will readily be understood that there is some shape and size of grain 
which would render the explosion the quickest possible. 
A charge made up of large-grain powder explodes more slowly than 
that made up of a small-grain powder; for although, on account of 
the larger interstices between the grains of the former, ignition is more 
rapid, yet the combustion of each grain is slower than in the latter 
case. The former is called a slow-burning powder (comparatively), the 
latter a quick-burning powder. It follows, then, that in order to secure 
uniform results with similar charges of powder, the size and shape of 
the grains must be as nearly as possible the same. 
The time of explosion is also affected by the density of the powder. 
* Vide “Short Notes on Gunpowder, and its Manufacture,” by Major Warded, R.A. 
