Carl,
I was not attempting to trap you, honestly, I just read this from Dahlgren's patent description:
"The body of the projectile when intended
to be used as a shot, may be made solid or
hollow. When intended to be used as a
shell, it must be made hollow, filled with
gunpowder or other suitable explosive material,
and fitted with a fuse in the usual
manner. In Fig. 2 a hollow projectile is
represented which may be used either as a
shot or shell.
The body of the projectile may be divided
35 into three parts, viz :—The middle which is
cylindrical,—the fore end which is conical,—
and the rear end, which may also be conical,
but I prefer to make it hemispherical. The
rear end of the body is made with protu-
40 berances (a' Fig. 3,) so shaped that when
the bottom is cast on the body, these protuberances
will be embedded therein and thereby
unite the two firmly together. The middle
of the body is cast with a series of ribs
45 a, projecting about one tenth (.10 in.) of an
inch from its surface. These ribs are to be
turned to a diameter two hundredths of an
inch (.02 in.) less than that of the bore of
the gun. The width of these ribs is about
50 eight hundredths (.08) of the circumference
of the projectile. These ribs I prefer to incline
to the axis of the projectile like the
threads of a screw, and to make their. inclination
to correspond in degree and di-
55 rection with the rifle grooves of the bore of
the gun out of which the projectile is to be
fired. The object of these ribs is: First,
to diminish the bearing surface of the projectile
. against the bore of the gun. Secondly,
by their oblique action against the air Co
during the flight of the projectile from the
gun, to assist in steadying it and in keeping
rt from deviating from the direction in
which the gun is aimed."
Of course this applies to a RML and not to a smoothbore.
John
