or 20 deg. at the end of a moderate range,
the velocity at starting must be low. Hence, for pieces intended for
breaching no enlarged powder chamber is wanted; the effect on the wall
is due to the shell, which must be made of a shape to hold the most
powder for a given weight; and, therefore, rather short and thick. This
gives us a large bore, which need not be long, as little velocity is
required.
For producing destructive effect among troops, a third kind of
projectile is employed. It is called shrapnel, and it consists of a thin
shell, holding a little powder and a large quantity of bullets. The
powder is ignited by a fuse, which is set to act during flight, or on
graze, when the shell is nearing the object. The explosion bursts the
shell open, and liberates the bullets, which fly forward, actuated by
the velocity of the shell at the moment of bursting. Hence, to render
the bullets effective, a considerable remaining velocity is requisite.
The gun must therefore take a large powder charge, while, as the shell
has to hold as many bullets as possible, the bore must be large enough
to take a short projectile of the given weight.
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