July-August - Air Defense Artillery School

38. THE COAST ARTILLERY JOUR:\AL
vidual talents of the gunner. In any case, the gunner is not
handicapped by the presence of the sights.
The principal advantage of sights is generally believed to
be obtained at the time of opening fire. The sights can be
brought up to line and then swung ahead to establish an
opening lead; the first tracers should then be line shots or
nearly so, and very near the target from the standpoint
of lead. A.djustments then made as a result of tracer observation
should be fairly small. If a simple ring sight is
used it will be necessary to establish the opening lead and
applY.it in target le,zgtlzs; this type of lead varies directly
with both range and target speed-the estimated number of
lengths must be applied by further estimation against the
open sky, there being no known form of successful sight
for laying off apparent target lengths. (Due to the amount
of estimation involved, plus the fact that no two types of
planes have exactly the same length, it is doubtful whether
or not such a device would be justified.)
If the forward area (multiple ring) type of sight is used
the opening lead will be taken in angular value, in terms of
mils. This type of lead also varies directly with the target
speed; however the variation due to different ranges is
almost negligible unless firing is done at extremely long
ranges. The forward area sight also constitutes a templet
for projecting the target's line of Hight and a measuring
device for actually applying the desired lead. Since the
necessary angular lead for any given angle of approach
depends practically on target speed alone, the concentric
rings of the front sight are designated in terms of target
speed in miles per hour, usually 100, 200, and 300, for the
three concentric rings. These values are correct for targets
at the midpoint of the course and a reduction in lead is
necessary for both approaching and receding targets. Forward
area sights are discussed in detail elsewhere.
Although machine gun sights are most valuable at the
time of opening fire, there are undoubtedly special conditions
where the sight may produce hits quickly without the
aid of tracer adjustment. Such may be the case when a
target dives directly at the gun. Such may also be the case
when a low-Hying maneuvering plane approaches the point
in a banked turn where the gunner is looking tangent to
the turn, the target appearing momentarily stationary. On
crossing courses the usual method is to look over or around
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