* * * * *

From the above it is seen that a manufacturer supplying both
armor-plate and shell to the Government is called upon to produce a
shell with sufficient integrity to completely penetrate, and without
breaking up, his armor-plate of sufficient thickness to resist that
shell.

The capping of projectiles consists in placing over the point a cone or
mass of metal of comparative softness. In the United States services
soft steel is used for the purpose. Authorities disagree as to the
exact function which the cap plays, some claiming it to act as a
lubricating metal facilitating the passage of the projectile, others
claim that it gives an initial shock to the armor-plate before the
shell proper has struck it, which latter then strikes the plate in a
state of molecular unrest, and, therefore, of impaired resisting power.
Firing tests of shell at armor-plate at oblique angles have proven the
capped shell superior, which would indicate that the cap in this
instance at any rate is capable of securing a hold on the plate which
the bare point of the shell cannot, in so much as uncapped shells
glance off. At any rate capped projectiles are, on the whole, superior
to the uncapped and the practice of capping is recommended as an
additional advantage when used in conjunction with the improvements
here-in-after described.

At a specified distance from the base of the shell a groove or
band-score is turned for the rotation band. For projectiles under
7-inches calibre, pure copper is usually employed, but for larger
calibre an alloy of 97-1/2 per cent of pure copper and 2-1/2 per cent
of nickel is used and is annealed before banding. The rough bands are
in a form of solid rings cut from drawn tubes or cylindrical castings,
and must be carefully hammered into the score or preferably pressed in
by hydraulic pressure and finally turned to proper size, shape, and
finish.

Their use has been previously described and the improvements in
armor-piercing shells hereinafter described are based upon a study of
the stresses sustained by a projectile upon impact while rotating about
its major axis at the high rotative velocity which the engaging of
these bands with the rifling of the gun has imparted to the shell.

The following table compiled by the author gives the rotative
velocities of various projectiles:

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