The caliber of any
firearm
is the measurement of the bore of its barrel. It could be measured
directly as the diameter of the bore, or some intermediate system could
be used as in the case of shotguns, where the caliber or gauge equals
the number of lead ball bullets of that diameter which could be molded
from one pound of lead. In the case of rifled firearms, the caliber is
the measured diameter between lands or grooves of the rifling (see the
picture). However, for many reasons actual (measured) caliber may differ
from the caliber designation. Most often this misnomer is based on
historical or marketing issues. Another source of complications is that
there are two measuring systems used worldwide – the
metric system
and the imperial or inch system. Metric calibers are measured in
millimeters, i.e. “7.65 mm” or “9 mm”; Inch calibers are measured in
hundredths or thousandths of an inch, with the omission of the leading
zero, i.e. “.30” or “.300” (0.30 inch or 7.62mm) or “.45” (0.45 inch or
11.43mm). The direct relationship between metric and inch calibers is
represented as 1 inch = 25.4 millimeter, or 1 millimeter = 0.039 inch.
In some cases, the nominal inch caliber is the same as the bore diameter
(between the lands), as in the case of many .30 caliber weapons that
have bore diameters of 0.30 inch or 7.62mm. In other cases, the nominal
caliber may match the
bullet
diameter (slightly wider than the bore) e.g. the .40 S&W. However,
in a few cases, the nominal inch calibers have no direct relationship
with actual bore or bullet diameter, as with .38 caliber rounds which
have bullet diameters ranging from 0.357 to 0.401 inches; these
cartridges retain their misleading designations from the age of
black powder revolvers.
Metric caliber designations tend to be more accurate, but may still
vary between whether bore (e.g. 7.62mm) or bullet (e.g. 9mm) diameters
are used.
Also, even if two firearms have exactly the same actual caliber, they
may use cartridges of very different size and power, i.e. Soviet TT
pistol and US M1 Garand rifle both have bores of 7.62mm diameter, but
their cartridges are very different in size and power. Therefore, in
most cases it is insufficient to know just the caliber of a firearm to
procure suitable ammunition, and some additional information needs to be
provided. The simplest way is to give any
cartridge
its own name, i.e. 9mm Steyr and 9mm Luger, or .357 Magnum and .357
SIG. In either case, the calibers (bullet diameters) are the same, but
the cartridge shapes, dimensions and power are different, and they are
NOT interchangeable. However, there are far too many cartridges to give
them all names, so the most convenient (and most common) way with metric
designations is to use the case length in conjunction with the caliber.
The typical designation that follows this pattern is 9x19, where “9”
means the caliber and “19” is the cartridge case length, both measured
in millimeters. If several cartridges of different properties have same
caliber and case length, some additional information must be provided,
usually in the form of a name or suffix, which distinguishes the shape
of case head. The sample of the “name” use is 9x23 Largo / Bergmann and
9x23 Steyr cartridges, which were independent developments but are
virtually indistinguishable in size and power. Another example is 9x23
Winchester, which, while having the same external dimensions as previous
two 9x23 cartridges, has thicker case walls and thus can withstand
heavier pressures; this cartridge can be easily loaded into firearm
designed for either of former cartridges, but to do so would be
extremely dangerous! Yet another example is a fourth cartridge with the
same caliber and case length, the 9x23SR, more generally known as .38
Super Automatic or simply .38 Super. This cartridge has semi-rimmed
case, that is, it has both the extraction groove and a diminutive rim,
as it was designed in around 1898 to be used both in semi-automatic
pistols and revolvers. Another example of similar designations but
different actual dimensions are 9x18 PM and 9x18 Police cartridges.
While these are identical in designations, actual calibers are
different, as the 9mm PM bullet has an actual diameter of 9.2mm, and the
9mm Ultra has an actual bullet diameter of 9.02mm. Therefore,
mismatching one such cartridge for another may be very dangerous for
both gun and shooter. The source of this mismatch is that most western
calibers are measured between the grooves of the rifling, and therefore
are same as actual bullet diameter; in Russia and USSR, some calibers
were measured between the lands of the rifling, therefore actual bullet
diameter is bigger than measured caliber.
Considering all said above, great care must be exerted when selecting proper ammunition for any firearm.
Bullet types
Many and various bullet types have been developed for fighting,
training and other applications; only the most common are mentioned
below.
Lead bullets are the oldest type and today used mostly in
revolver and small-bore rimfire ammunition. These are formed from lead,
or more often, an alloy of lead and antimony. Such bullets are
inexpensive but usually can’t withstand higher velocities, and produce
significant lead fouling in a rifled bore during prolonged use.
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LRN - Lead Round-Nose bullet |
LHP - Lead HollowPoint bullet |
LSWC - Lead Semi-WadCutter bullet |
LWC - Lead WadCutter bullet |
Jacketed bullets are the most common and are the only available for
military weapons
due to international treaties. Such bullets are designed using a lead
core that is enclosed by a gilding-metal jacket. These bullets are known
for good penetration, but stopping power is often less significant than
that of expanding bullets. Jacketed bullets are sometimes referred as
“ball” bullets on historical grounds.
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|
FMJ - Full Metal Jacket bullet (also known as 'ball' bullet) |
Expanding bullets include
Hollow-point and
Soft-Point bullets.
Hollowpoint bullets are currently the most popular choice for police
and self-defense ammunition. Such bullets are designed with the hollow
cavity in the nose (therefore the common name “hollowpoint”). This
cavity causes the bullet to expand once it hits the soft tissue of human
or animal body; thus results in reduced penetration but a wider wound
channel. Softpoint bullets do not have the cavity in the nose but the
lead core is exposed at the tip so bullet can easily deform in the
target to provide larger wound channel.
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|
JHP - Jacketed HollowPoint bullet |
SJHP - Semi-Jacketed HollowPoint bullet |
SP - Soft-Point bullet |
Armor-piercing pistol ammunition is nowadays mainly intended for
use against adversaries with body armor. The simplest AP bullets for
handgun ammunition are usually made from solid brass or bronze;
sometimes these bullets are made with pointed tips to further improve
penetration. Since such bullets, because of their hardness, may cause
excessive wear to the barrel, they may be covered with some a softer
materiel, such as Teflon. In some cases, AP bullets are made with the
traditional soft brass or other gilding-metal jacket and with a
composite core, made of a hardened steel penetrator together with some
other filler. One example of such ammunition is the Belgian FN 5.7mm
SS190 bullet, which has core made partly of steel (front) and partly of
aluminum (rear). Another example is the Russian 9mm 7N21 bullet, which
has a hardened steel core that passes throughout entire bullet and is
exposed at the tip; the space between the jacket and core is filled with
polyethylene.
7.62x38R Nagant
Developed during 1890s, this cartridge was especially designed for
Belgian Nagant revolvers which featured unique gas-seal action. The
bullet is seated deep into the cartridge case, and prior to firing the
cylinder of the revolver moves forward, so the cartridge mouth enters
the barrel to provide gas seal between the cylinder and bore. It was
extensively used in Russia and USSR, as well as in Poland. Today this
round is obsolete.
|
Designation |
Manufacturer |
Bullet weight, g |
Muzzle velocity, m/s |
Muzzle energy, J |
Comments |
|
FMJ |
|
7 |
270 |
255 |
flat-nose bullet deeply seated into the case |
.38 Smith & Wesson (.38 SW)
Developed by famous company Smith & Wesson, this revolver cartridge
was introduced in 1877 and over the following decades it was widely
popular for compact revolvers. During WW2, a 'ball' (FMJ) version of
this round was issued to British troops as .380/200 revolver cartridge. A
slightly different version of the same round was also known as the .38
Colt New Police. Today this round is mostly obsolete.
|
Designation |
Manufacturer |
Bullet weight, g |
Muzzle velocity, m/s |
Muzzle energy, J |
Comments |
|
LRN |
Remington |
9.4 |
208 |
205 |
|
.38 Smith & Wesson Special (.38 SW Special)
This cartridge was introduced in 1902 as a stretched, more powerful
version of the older .38 SW cartridge. It quickly became very popular in
USA, and during better part of the 20th century it was the most widely
used revolver cartridge there, for both civilian and police
applications. It was also issued to certain military personnel, most
notably to USAF and USN pilots during 1950s and 1960s.
It is still quite popular and is currently produced by many ammunition
manufacturers worldwide in a large number of versions, with loadings
especially intended for target shooting, practice or self-defense. It
must be noted that modern 'high pressure' rounds, usually marked with +P
suffix, are NOT suitable for older revolvers, designed for standard
pressure loadings.
|
Designation |
Manufacturer |
Bullet weight, g |
Muzzle velocity, m/s |
Muzzle energy, J |
Comments |
|
JHP |
Remington |
7.12 |
290 |
299 |
modern loading |
|
JHP +P High Velocity |
Federal |
8.36 |
290 |
346 |
modern high pressure loading with Hydra Shok bullet |
|
LSWC +P |
Remington |
10.2 |
270 |
374 |
modern high pressure loading |
.357 Magnum
This round was created in around 1935 as a joint effort between Smith
& Wesson and Remington to produce more powerful revolver round for
American law enforcement. It caught up from the start and is still
extremely popular for most practical purposes - sport shooting,
self-defense, hunting. Over the time, quite a few carbines (mostly
lever-action type) were also chambered for this round, and few
semi-automatic pistols were built to fire it. Today .357 Magnum is
produced by many ammunition manufacturers worldwide and in great many
loadings.
|
Designation |
Manufacturer |
Bullet weight, g |
Muzzle velocity, m/s |
Muzzle energy, J |
Comments |
|
Golden Saber JHP |
Remington |
8.1 |
372 |
560 |
|
|
Express JHP |
Remington |
8.1 |
442 |
792 |
|
|
Hydra-Shok JHP |
Federal |
10.23 |
378 |
727 |
|
|
Express SP |
Remington |
10.23 |
376 |
723 |
|
|
Express JHP |
Remington |
11.66 |
350 |
714 |
Muzzle velocity shown from long (8") barrel |
.41 Magnum
The .41 Magnum was created in 1964 to fill the gap between .357 Magnum
and .44 Magnum rounds. This round failed to achieve high popularity of
its older magnum-class 'neighbors' but still has a strong, although
small, following among revolver shooters. It is still produced by
several major ammunition manufacturing companies.
|
Designation |
Manufacturer |
Bullet weight, g |
Muzzle velocity, m/s |
Muzzle energy, J |
Comments |
|
Silvertip JHP |
Winchester |
11.34 |
380 |
825 |
|
|
Express JHP |
Remington |
13.6 |
396 |
1070 |
|
.44 Smith & Wesson Special (.44 Special)
This round was created by Smith & Wesson in 1907 as a stretched-out
and more powerful version of the older .44 Russian round. Originally a
black-powder number, it was soon converted to
smokeless powder and is still produced in this form. This round is still popular for target shooting and self-defense.
|
Designation |
Manufacturer |
Bullet weight, g |
Muzzle velocity, m/s |
Muzzle energy, J |
Comments |
|
Silvertip JHP |
Winchester |
12.96 |
274 |
490 |
|
|
LRN |
Winchester |
15.55 |
229 |
408 |
|
|
Express LRN |
Remington |
15.94 |
230 |
421 |
|
.44 Magnum
When first introduced in 1956 as a joint effort between Smith &
Wesson and Remington, this revolver round was advertised as a most
powerful handgun cartridge in the world. While it is no longer holds
this title, being outperformed by a number of monstrous loads of larger
caliber, it is still a formidable number, suitable for a number of
applications including long-range target shooting, self-defense
(especially against dangerous animals) and hunting. Several
semi-automatic pistols and carbines (lever-action and semi-automatic)
were produced over the years to fire this cartridge. Today it is still
manufactured by a number of makers worldwide.
|
Designation |
Manufacturer |
Bullet weight, g |
Muzzle velocity, m/s |
Muzzle energy, J |
Comments |
|
Express JHP |
Remington |
11.66 |
490 |
1409 |
|
|
Hydra-Shok JHP |
Federal |
15.55 |
360 |
1006 |
|
|
Core-Lockt JHP |
Remington |
17.82 |
376 |
1266 |
|
.45 Colt (.45 Long Colt, .45 LC)
This is one of the oldest revolver cartridges still in production
today. It was introduced in 1873 along with famous Colt Single Action
Army revolver, and was adopted by US military. Originally a strictly
blackpowder loading, today this round can be found in both blackpowder
versions (for old revolvers) and in smokeless loadings for modern
revolvers and carbines.
The alternate (and unofficial) designation .45 Long Colt (or .45LC in
short) comes from relatively recent times, to distinguish it from
another .45caliber military revolver loading of the 1875 era, the .45
Shofield, which featured shorter case and lighter charge.
|
Designation |
Manufacturer |
Bullet weight, g |
Muzzle velocity, m/s |
Muzzle energy, J |
Comments |
|
LRN |
|
16.2 |
274 |
610 |
original black powder load of 1873 |
|
Silvertip JHP |
Winchester |
14.58 |
280 |
575 |
modern smokeless load |
|
Express LRN |
Remington |
16.2 |
262 |
558 |
modern smokeless load |
.455 Webley
The .455 Webley Mk.I ammunition was adopted by British army in 1887.
With introduction of the cordite propellant this round was changed to
.455 Mk.II with slightly longer case, which was also used for latter
versions (Mk.III to Mk.V), which featured different bullets. All .455
revolver ammunition was officially declared obsolete by British military
in around 1950. Some manufacturers still produce this ammunition for
older guns, although no new guns were made for these loadings for quite
some time.
|
Designation |
Manufacturer |
Bullet weight, g |
Muzzle velocity, m/s |
Muzzle energy, J |
Comments |
|
.455 Mk.I |
|
17.7 |
213 |
390 |
original black powder load |
|
.455 Mk.II |
|
17.2 |
177 |
268 |
original cordite loading of WW1 era |
|
.455 Mk.II |
Fiocci |
16.9 |
259 |
566 |
modern commercial loading |
.500 Smith & Wesson Magnum
The .500 SW Magnum is most recent and most monstrous revolver
magnum-class round. It is chambered in specially designed S&W
X-frame revolvers and several carbines. The most obvious purposes for
this round are hunting and protection from large and dangerous animals
such as grizzly bears.
|
Designation |
Manufacturer |
Bullet weight, g |
Muzzle velocity, m/s |
Muzzle energy, J |
Comments |
|
JHP |
Corbon |
22.68 |
488 |
2700 |
|
|
LRN |
Corbon |
28.5 |
495 |
3500 |
|
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