Modern antiaircraft guns are more than mere engines of destruction: they are
complicated pieces of mechanism that require constant care and supervision. The
following data on the maintenance of antiaircraft guns in the combat areas are
taken from a translation of an article appearing in a German publication.
* * *
The gunners of the antiaircraft batteries watch the barrels of their guns with the same
diligence that the infantryman does his rifle. But this care does not suffice to preserve
that fine precision which is the essential thing in the case of the antiaircraft gun. From
time to time the initial velocity valves must be measured and tested. It will be remembered
that velocity expresses the ballistic velocity at zero meters, that is, on leaving the barrel
of the gun. This must be very familiar to the gun commander.
It is necessary to know the initial velocity value of each gun in order to accurately
fire the guns so as to have the shells burst in a definitely prearranged target area.
There are fixed stations in Germany for the measuring and testing of the initial
velocity valves and in combat areas there is a motorized "initial velocity detail" which
goes from one antiaircraft regiment to another to test every gun.
Magnetized projectiles are fired through two coils that are constructed at an accurately
measured distance from the barrel of the gun. The time needed by the projectile to go from
the first to the second coil is determined by the "Boulanger apparatus", two of which, in a
special trailer, are attached to the initial velocity testing detail. As the projectile
passes through the coils, its magnetic field generates a magnetic impulse which (over a
relay) releases two falling weights, one after the other, in the Boulanger apparatus. The
second and smaller weight activates an impact measurer which makes a notch in the first
weight. The height of the fall is measured by a gauge. By these measurements the existing
initial velocity value for each gun is determined.