r trajectory is
that it holds more ground under its fire. For example, take our
service rifle: At a range of 500 yards, the bullet, at the highest
point in its trajectory or line of flight, is 2 feet above the line of
sight. It is, therefore, apparent that if the bottom of an object 2
feet or greater, is aimed at, it would be struck if it were anywhere
under 500 yards. Now, take a rifle with a very curved trajectory, say
one whose bullet, at the highest point of the trajectory corresponding
to a range of 500 yards, is 10 feet above the line of sight. There
will be a large extent of ground between the target and the rifle that
is not danger space for a target 2 feet above the line of sight.
Hence, we see that the rifle with the flatter trajectory is better.

The continuous danger space afforded by the flat trajectory of our
service rifle enables us to adopt a universal sight for all ranges up
to 500 yards,--that is, the battle sight, which is the rear sight
ready for use when the sight leaf is laid down.

=1411. Cone of fire or cone of dispersion.= If a body of soldiers fire
at the same target the bullets will not, of course, follow the same
path, but will be scattered. This is due to differences in sights,
parts of the rifle, ammunition, and to a greater extent, to the
individual errors of the soldiers in aiming and firing.

The trajectories or paths of the bullets considered together form a
horn-shaped figure or cone, called the _Cone of fire_ or cone of
dispersion. (See Fig. 44.)

[Illustration: Fig. 44]

=1412. Shot group and center of impact.= If the _cone of fire_ be
intercepted by a target (for example, A O, Fig. 44) at right angles to
the axis of the cone, the shot holes will make a pattern or group
called the _shot group_, the holes being the thickest approximately in
the center of the group, called the _center of impact_. From this
point in all directions the density of the grouping decreases
progressively,--at first gradually, then more rapidly, out to the
limits of the group.

Naturally, the size of the cone of fire and of the shot group vary
with the skill of those firing, good shots making a small cone and
small group, and poor shots a large cone and large group.

=1413. Beaten zone.= The intersection of the cone of dispersion with
the surface of the ground is called the _beaten zone_.

If the surface of the ground is horizontal, the form of the _beaten
zone_ is that of an ellipse with its longer