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O N TA R G E T • •
What does my
calibre name mean?
JAN-LODEWYK SERFONTEIN
W
ay before guns were
designed and manufac-
tured, other weapons were used
for survival and to conduct war.
Knives, spears and a bow and
arrow are but a few of the weap-
ons used over time. Like guns,
other weapons also had names
and descriptions to identify them.
The long bow, short bow and the
recurve bow are examples of such
descriptions.
In the 17th century in North
America, the guns used were
longer than 6 foot and not very
accurate. During the 18th century
guns were designed in Europe
which seldom had barrels longer
than 30 inches. The barrels had
between 7 and 9 grooves with a
slow turn.
During the 18th century com-
munication and standards were
not well developed and a number
of new guns and calibres were
designed on two different con-
tinents. Since the 18th century
a similar way of naming new
calibres has been used. At present
there are two organisations which
list and test calibres, but the
organisations use similar naming
methods.
When a calibre originating from
Europe is named, two measure-
ments are used, together with
a name. The first measurement
is the diameter of the bullet in
millimetres and the second mea-
surement is the length of the
casing. The name mostly refers
to the original manufacturer of
the calibre. For instance, a 7 x 57
Mauser bullet is 7 mm in diame-
ter. Its casing is 57 mm long and
the Mauser factory designed the
calibre. ent diameter holes can be seen - X
being the bore diameter and Y
being the groove diameter.
Weapons which originated in
America are named by using
one measurement and a name.
The length is in inches. A .243
Winchester bullet is .243 inch
in diameter and designed by the
Winchester factory. It is important
to note that the diameter of the
bullet is .243 of an inch and not
243 inches. A FEW INTERESTING CALIBRE NAMES
• 30-06 Springfield: .300 Bore
diameter bullet developed in
1906.
• 25-06 Remington: .30-06
Springfield casing downsized to
be able to shoot a .257 caliber
bullet.
• 308 Winchester: Also known
as the 7.62 x 51 since its bore
diameter is 7.62mm and its
length 51mm.
• 7mm-08 Remington: .308
Winchester casing downsized
to be able to shoot a 7mm cali-
bre bullet.
• 22-250 Remington: 250 Savage
casing downsized to be able to
shoot a .224 calibre bullet.
But why does my 308 Winchester
and my 300 Winchester Magnum
use the same diameter bullet? And
why is the diameter of my 303
bullet more than the diameter of
my 308 bullet?
Looking at the next cross-section
of the barrel of a gun, two differ-
The diameter of the bullet used in
the name of the calibre, can be the
groove or bore diameter. In the
case of the .303 the bore diameter
was used. In the case of the 308
Winchester, the groove diameter
was used to describe the diameter
of the bullet. In the case of the
300 WM, the bore diameter was
used for the name of the calibre.
Be careful of the 6.5-284 Norma
- the .284 casing was designed
in America by Winchester. Later,
in Europe, Norma downsized it
to a 6.5mm calibre bullet, being
the reason for the 6.5mm and the
.284 inch in one name!
SENWES Scenario • APRIL/MAY 2017
51