projectile must be designed not only to penetrate, as
well as to withstand the great compressional stresses upon the
advancing head of the shell but the body of the shell must be so
designed as to give a maximum of integrity. The torsional stresses act
along _ed_, and in order to resist these stresses the shell must be so
designed that the resisting ability will be increased along that line,
re-acting along _de_.

This the author advocates by means of a "twist forging," in which the
grain of the metal will lie co-incident with the lines of the torsional
stresses, and by the introduction of spiral ribs lying co-incident also
with the lines of the torsional stresses and the grain of the "twist
forging" manufactured by a process indicated in the patent herewith
appended. By the introduction of the spiral ribs it will be seen that
each disc is reinforced to withstand the tendency of the disc behind to
crowd upon it and that by means of a properly designed shell of this
type the whole energy of the shell can be better transmitted to the
point of impact by means of the spiral ribs and twisted grain.

Furthermore, should any flaws be present in the ingot, their size would
be reduced by the twisting, as are the spaces between the strands of a
rope when twisted in the proper direction for so doing. Also, with a
flaw in a finished projectile, and lying in a spiral direction the
result of the compression stresses would be to jump across the flaw or
to decrease the gap instead of acting wedgelike along the flaw causing
it to open as before mentioned. Finally, an increase in integrity means
an increase in penetrability, or in the percentage of complete
penetration, with the ultimate necessity of increasing the thickness of
armor-plate to successfully exclude the improved armor-piercing shell.

No. 863,248. PATENTED AUG. 13, 1907.

C. DE ZAFRA.

PROJECTILE.

APPLICATION FILED DEC. 10, 1906.

[Illustration: FIG. 1.]

[Illustration: FIG. 2.]

[Illustration: FIG. 3.]

[Illustration: Witnesses
[Names are illegible]

Carlos de Zafra Inventor

By his Attorney Hensey Gough

United States Patent Office

CARLOS DE ZAFRA, OF NEW YORK, N.Y.

Projectile

No. 863,248

SPECIFICATION OF LETTERS PATENT. Patented Aug. 13, 1907.

Application filed December 10, 1906, Serial No. 347,055

_To all whom it may concern:_

Be it known that I, CARLOS DE ZAFRA, a citizen of