ELIMINATING SUSPECTED ARMS

While the ‘engravings’ are the
actual ‘‘signatures’ ‘of the particular
arms, there are other factors which
may eliminate -a suspected weapon
before the microscopic examination
is made. The number of lands and
grooves in rifles and automatic pis-
tols, as well as revolvers, vary in

Two .22 calibre bullets in a recent attempted
murder case. Photograph taken through
eyepiece of comparison microscope.

accordance with the manufacturers
specifications. We find that some
weapons have only two grooves while
others have eight. There are also
others which have four, five, six and
seven grooves. Thus the number of
grooves on a bullet may at once
eliminate a given weapon. If a bullet
is found with six groove engravings,
and the weapon is found to have
eight grooves, then it can be discarded
at once. Another, and even more
obvious method of elimination is by
the caliber. If a bullet is found which
is obviously a .45 caliber, it could
not be fired from a .38 revolver, and
the weapon can be eliminated.

Another interesting feature in
rapid elimination, is the direction of
twist or rifling. It has already been
mentioned that some weapons have
a right hand and some a left hand
twist. Here again it is useless to con-
tinue with an examination when the
bullet is found to bear marks of a
twist in different directions to that
of the suspected arm.

Accordingly we find the examiner
can make a quick determination by
caliber or diameter of the bullet, by
the number of grooves and lands,
and by the direction of twist of the
rifling. This quick determination
naturally presupposes that the bullet
is not too badly deformed. If the
bullet has struck some hard object it
may be flattened out, or sheared off
On one side. In cases such as these the
eXaminer must redouble his efforts,
and often weighs the bullet to deter-
mine its probable caliber and type.
Bullets of the same caliber often

NINETEENTH EDITION

differ in weight according to the
kind of ammunition and its purpose.
The grease groove and the ‘‘cannel-
ure,’ or that portion of the bullet
which is crimped with the cartridge
case, are also of use in arriving at
the type of ammunition to which the
bullet belongs.

While the bulk of firearms identi-
fication work deals with bullets, a
very important branch of this science
concerns cartridge cases. Frequently a
cartridge is found at the scene of a
crime, which has been pumped out
of a rifle or ejected by an automatic
arm, or perhaps a revolver has been
carelessly unloaded and the cartridges
left where they fell. The cartridges
so found can nine times out of ten,
be definitely shown to have been
fired from a specific weapon. As pre-
viously mentioned, all machine work
in the weapons bears characteristic
marks entirely individual to that
weapon and no other. The cartridge
case found discharged has been sub-
jected to a pressure of many tons per
square inch in the chamber of the
arm when it was fired. This has
driven the soft brass into tight con-
tact with the breach of the weapon
and left tiny markings on the case.
Besides this, the cartridge is forced
backward with violence at the instant
the bullet leaves it, so all the markings

.22 caliber bullets in a recent attempted
scope, illuminated with spectal
microscopic lamps.

Two

on the breach block of the arm or on
the bolt head, will be shown as en-
gravings on the base of the cartridge.
In fact, the soft copper or brass
primer in the center of the cartridge
is slightly bulged outwards by the
tremendous pressure and_ flattened
against the breach at the instant of
firing. The primer contains the mix-
ture which explodes on percussion
of the firing pin. Formerly a fulmin-
ate of mercury mixture, the primer
mixture is now frequently made with

RUNETCRIEF
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Harry Bugg
FANNY BAY

V.I., B.C.

Fairway Grocery

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B.C.

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Three Miles North of Courtenay,
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Headquarters for the
Ancient Order of the “Peach”

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Page Thirty-three