In relation to rifled weapons, caliber is a numerical expression of the diameter of the bore, measured between opposing fields, or (which happens much less often) rifling. Even less common is measuring the rifling and rifling field of the bore that are opposite to each other. In most countries, the caliber of a rifle is expressed in millimeters and fractions thereof (usually accurate to the second decimal place when written as a decimal).

In the UK and the USA, as well as in countries where the English system of measures is adopted, the caliber is indicated in fractions of an inch - in thousandths in the UK and in hundredths in the USA, and the written designations have a peculiar form - decimal written as an integer with a dot in front (for example, the caliber designation is “three lines” - 0.3" = 7.62 mm, looks like .30 or .300).

The caliber is also indicated in lines, the ratios are as follows: 1 "= 25.4 mm, 1 line = 2.54 mm; and in points: 1 inch = 10 lines = 100 points. Thus, the three-line SI rifle. Mosin has a caliber 3x2.54 = 7.62 mm, and the calibers of the three lines, .30, .300, 7.62 are equal to each other. Lately In England and the USA there is no dot before the designation of calibers.

For example, US caliber 30 should be multiplied by 0.254, and English caliber 300 by 0.0254g. As a result, we obtain that US caliber 30 is equal to 30 x 0.254 = 7.62 mm, and English caliber 300 is equal to 300x0.0254 = 7, 62 mm. Similarly, caliber 410 corresponds to 10.41 mm.

In rifled weapons, the diameter of the bore is measured either by the rifling or by the margins. Therefore, the same caliber can be designated differently. Thus, the 9 mm caliber of the “Los” carbine is designated by the margins (9 mm), and the TOZ-55 “Bison” caliber is designated by the rifling (9.27 mm). The caliber of a 5.6 mm rifle is sometimes designated as 5.45 mm: the first is a change in caliber by rifling, the second by margin. The 7.62x53R three-line cartridge has a leading bullet diameter of 7.92 mm. In general, in traditionally domestic cartridges the diameters of the leading parts of the bullet are larger than the caliber. The diameters of bullets for rifled weapons always exceed the diameters of the bores (for the possibility of cutting into the rifling and acquiring rotational motion). The excesses of bullet diameters over the diameters of the bores are far from the same, since they depend on many reasons (depth, shape and number of rifling, bullet hardness, length of its leading part, quality of gunpowder, and others).

It is clear that from the mentioned several numbers obtained with different dimensions diameters of the bore of the rifled barrel, as well as the diameter of the bullet, only one will correspond to the designated caliber. Typically this number refers to one of the dimensions of the bore, so the designated caliber of rifle ammunition is essentially the caliber of the weapon for which the ammunition is intended. The actual dimensions of the bullets never correspond to the designated caliber. Only in cases where the caliber of a weapon is measured by rifling do the designated calibers of the weapon and the true diameters of the bullets turn out to be very close to each other, close, but still different. It should be added to the above that among the caliber designations there may be those that do not correspond to the size of either the weapon or the bullets. They are simply traditional and do not act as information about size, but as a symbol of a particular cartridge. As a result, it is accepted in world practice mixed system designations, in which a given cartridge is designated as it was designated in the country that issued it.

Perhaps the only one prerequisite is the presence in the name or designation of the cartridge of information about its caliber. Typically, caliber designations in the inch system are not translated into millimeters, since they are often either approximate or conditional, being only a symbol of a given cartridge, and not a carrier of information about the true size of the caliber. So, when formally converting, for example, designation 38 into millimeters, the value obtained is 9.65 mm. But this is a non-existent caliber - a symbol. 38 is actually a 9 mm cartridge used in weapons with a true caliber of 8.83 mm. Perhaps only specialists know that the .38 Special revolver cartridge uses .357 caliber bullets. main reason The discrepancy, as mentioned above, lies in measuring the diameter of the barrel bore - by rifling or by margin.

Strictly speaking, the caliber of a cartridge is the caliber of the weapon for which the cartridge is intended to be fired. The caliber of the bullet itself almost never coincides with that indicated in the name of the cartridge, since its diameter is always greater than the diameter of the gun barrel, measured “along the margins”. For most cartridges developed in Europe, their name includes the numerical value of the caliber in millimeters, and for cartridges created in the USA and England, the name indicates the caliber in hundredths or thousandths of an inch. Although there are exceptions to this rule. For example, the purely European cartridge .30R Blaser (.30 Air Blaser) received a typical Anglo-American designation, and in the name of the American cartridges 7 mm Remington Magnum (7 mm "Remington Magnum") and 7mm-08 Remington (7 mm-08 "Remington") 19 gauge is indicated according to European traditions - in millimeters.

In the name of European cartridges, in addition to the caliber in millimeters, the length of the cartridge case in millimeters and its type are usually indicated - 7x64, 7x65R, 7x57R. The letter R means the presence of a protruding edge - a flange. Often in catalogs they add the name of the developer company - 7x64 Brenneke, 7x65R Brenneke. The designation of Russian cartridges is also based on this principle, however, as mentioned above, in domestic cartridges the diameters of the leading parts of the bullet are larger than the caliber. So, our 7.62x39 mm cartridge is actually loaded with 7.87-7.92 mm bullets, with the exception of its variants produced in the USA, which use regular bullets with a diameter of .308, i.e. 7.62 mm.

A certain specificity is found in the designation of old large-caliber (big bore) English cartridges for smoky and smokeless powder. Since all of these cartridges were rimmed, the case type designation was not indicated. Thus, .450-3 1/4 Rigby denotes the caliber in thousandths of an inch (.450), the length of the case in inches (3 1/4) and the company that produced this cartridge and/or weapons for it.

The .577 Nitro Express cartridge (3"&2 3/4") had two loading options - in a 3-inch (76.2 mm) long case and in a 2 3/4-inch (67.7 mm) long case.

In the designation of American and English cartridges there is no information about the length of the cartridge case, and the numerical designation of the caliber is followed by the name of the developer: .375 A-Square, .300 Dakota, .300 Holland & Holland, .308 Winchester.

Caliber and name of the designer who created this cartridge. More often found in the designation of American cartridges. Thus, one of the most powerful hunting revolver cartridges is the .454 Casull (.454 “Casull”) created by Richard Casull, or the rifle .300 Jarrett (.300 “Jarrett”), developed by Kenneth Jarrett. The name of Weatherby's most famous cartridge, the .300 Weatherby Magnum (.300 Weatherby Magnum), contains both the name of the company and the surname of its developer, Roy Weatherby.

Double hyphenated designations are historically common in American cartridges. So, in the days of black powder (practically until 1890), in type designations .44-40, .45-70, the first number showed the nominal value of the caliber, and the second - the amount of black powder charge in grains (1 grain = 64.8 mg). However, the first American rifle cartridge for smokeless powder, .30-30, created in 1895, also retained this principle in its name. The most notable exception to this rule was the famous cartridge .30-06 Springfield (.30-06 “Springfield”), in the designation of which the numbers 06 indicate the date of its adoption by the US Army - 1906.

Most modern dual designations are due to the fact that a particular cartridge was created from an existing cartridge case. The creators of such ammunition are often single designers - enthusiasts who produce them in limited quantities for use in weapons of their own systems. (So-called "wildcat" cartridges). For example, the .25-06 is a cartridge with a nominal .25 caliber, created on the basis of a .30-06 cartridge case, compressed for a .257 diameter bullet. The .22-250 cartridge with a .22 caliber bullet is created on the basis of the .250 Savage (.250 Savage) cartridge case. The designation of the new cartridge .30-378 Weatherby (.30-378 "Weatherby") refers to another cartridge - .378 Weatherby (.378 "Weatherby"), the sleeve of which was used as the base.

When creating the 7mm-08 Remington cartridge (7mm-08 "Remington"), loaded with bullets with a diameter of .284, a recompressed .308 Winchester case (.308 "Winchester") was used.

England uses its own designation system for “converted” cartridges, which is completely opposite to the American one. If the American cartridge .338-.378 Weatherby Magnum has a caliber .338 and is created on the basis of a re-compressed cartridge case of the .378 Weatherby Magnum cartridge, then the British would call such a cartridge .378/.338. The English cartridge .500/.465 Nitro Express is a .465 caliber cartridge that uses a re-compressed .500 NE cartridge case, similarly the .500/416 designates a cartridge with a .416 Caliber bullet based on a .500 NE cartridge case. Express (Express) and Nitro Express (Humpo Express).

Some English cartridges have two versions of equipment: a less powerful one with black powder, intended for old guns, and a more powerful one with smokeless powder, intended for modern, more durable weapons. The latter variants are designated Express or Nitro Express, which indicates that such a cartridge throws a bullet as fast as the train of the same name rushes.

Particularly powerful cartridges that, when fired, develop excessively in the bore of a weapon high pressure powder gases, have the definition Magnum (“Magnum”) in their name: .222 Remington Magnum, .300 Winchester Magnum, .338 Lapua Magnum (.338 “Lapua Magnum”). Until the early 1980s, the word "magnum" was usually present in the designation of cartridges, especially American ones. Modern magnums and ultramagnums may not have these names, designers, but only assign figurative names to them (300 Pegasus) or their own names and initials (300 Jarret, 375 JRS).

Also, at present, it is already difficult to assert that the so-called “search” design of the sleeve is a prerequisite for including a cartridge in the magnum group with the assignment of the term “magnum”. Two other criteria play a significantly larger role - pressure and bullet speed. Some European high-velocity magnum cartridges have the letter 5 in their designation: 5.6x61SE, 6.5x68S, 8x68S.

Some designers give their cartridges fancy proper names, like .300 Pegasus, .338 Excalibur and .577 Tyrannosaur (cartridges by Arthur Alfin, A-Square), apparently wanting to emphasize their unique speed and power. Abbreviations in names. When writing to save space (especially when marking on case heads), abbreviations are often included in the designation of cartridges. For example, the name of the revolver cartridge .44 Remington Magnum (.44 "Remington Magnum"), due to its wide popularity and the absence of similar competing cartridges in production, is increasingly being shortened to .44 Magnum or simply .44 Mag. The names of well-known companies that are present in the official designation of the cartridge are also usually abbreviated: Winchester - Win, Remington - Rem, Weatherby - Wby.

As we see, various systems notations are very arbitrary and therefore do not allow one to calculate real opportunities cartridge, based on its name. It happens that a large caliber cartridge with a long case, like the 9.3x72R, in fact turns out to be not at all as powerful as one might expect. The energy of its bullet at a distance of 100 m from the muzzle is three times lower than that of a bullet from a much smaller caliber .300 Weatherby Magnum cartridge (.300 Weatherby Magnum). The difference is about 3500 J, which is comparable to the muzzle energy of the .308 Winchester cartridge (.308 Winchester).

Over time, the concepts of “weapon caliber” and “cartridge caliber” became more comprehensive, expanding to the full designation of the cartridge. This is quite logical, since different models of weapons with barrels of the same caliber can, differing in the shape of the chamber, be designed to use completely different cartridges with cartridges of different sizes and shapes. Therefore, the purely digital designation of the caliber, without the additions usually accompanying it, is now used only in relation to the bullet itself. Instead of the vague formulation “hunting carbine of 7.62 mm caliber”, another, more accurate and informative one is increasingly being used - “carbine (or cartridge) of 7.62x51 caliber”.

As is known, cartridges of the same caliber, even with the same diameters of the leading parts of the bullets, but with sleeves of different sizes and shapes, with flanges or grooves near the bottom, are absolutely non-interchangeable. In addition to the discrepancy between the cartridges, the non-interchangeability of cartridges is associated with the amount and type of gunpowder. Thus, the amount of gunpowder determines the pressure of the powder gases at strictly defined values ​​of the weight and diameter of the outer part of the bullet, the diameters of the rifling and fields of a particular gun, and the material of the bullet shell. For example, the nitroglycerin spherical powder used in the 7.62x51 cartridge cannot be used to reload 7.62x53R cartridges. Nitroglycerin spherical powder in a 7.62x51 cartridge with a semi-jacketed bullet weighing 9.7 g raises the pressure of the powder gases when fired to 3400 kgf/cm2. If this charge is poured into a 7.62x53R case, which uses a bullet weighing 13 g, then the pressure will rise even higher and can destroy the weapon. Weapons chambered for 7.62x53R are designed for operating pressures no higher than 3150 kgf/cm2.

Hunters should be aware that bullets for the same caliber of rifled weapons are in many cases not interchangeable. So, the diameter of the barrel bore along the rifling is domestic weapons for the 7.62x51 cartridge is 7.83 mm, and for the 7.62x53R cartridge the diameter of the leading part of the semi-shell and combat bullets is 7.92 (the diameter of the bore along the rifling for this cartridge is also 7.92), that is, larger. If a 7.62x53R hunting semi-jacketed or combat bullet is removed and inserted into a 7.62x51 cartridge, this will cause a sudden surge in pressure when fired, which in turn can lead to destruction of the weapon. Considering that the semi-jacketed bullet of the 7.62x53 cartridge weighs 3.3 g more, then such a shot is life-threatening. Foreign manufacturers always indicate the diameter of the bullet.

Trofimov V.N., Trofimov A.V. “MODERN HUNTING AMMUNITION for rifled weapons. CASES, POWDER, CAPSULES, BULLETS, CARTRIDGES, BALLISTICS ELEMENTS"

Caliber is the main parameter of both weapons and cartridges. Figuratively speaking, caliber is size. For example, caliber 9x18. What does this mean? This means the length of the cartridge case is 18mm, the diameter of the cartridge case (where the bullet is located) is 9mm. Or 5.45x39: means the bullet diameter is 5.45mm and the case length is 39mm.

Don't get confused by the definitions:

A cartridge case is an object where a charge of gunpowder and a primer are located (a device that ignites gunpowder upon impact)

A bullet is an object made of lead, steel or other materials that, after being fired, flies out of the weapon and hits the target.

A cartridge is a combination of a cartridge case and a bullet, that is, a bullet installed in a cartridge case.

Basic ammo and weapons you will encounter.

1. Caliber 9x18

These are PM pistols (Makarov pistol), the most common pistol in Russia, Ukraine, Belarus and other countries former USSR. This pistol has been in service for more than 50 years in all services: police, security, armed forces, etc. With this pistol you can confidently hit a person at a distance of up to 50m in unprotected parts of the body.

Also, cartridges of this caliber are used in some domestic submachine guns and special-purpose pistols. I won’t talk more about this weapon, since it is not very widespread, but you can get acquainted with these weapons in the games listed above.

2. Caliber 9x19

This is the most common pistol caliber in Europe and the USA. The most common pistols of this caliber are Glock -19. Also, many submachine guns, both foreign and domestic, are made for this cartridge. Cartridges of this caliber have great power, so they are guaranteed to hit an unprotected person at a distance of 100-150m, and at a distance of up to 50m they can also penetrate light body armor.

3. Caliber 5.45x39

This is a domestically produced automatic cartridge. Currently in service with Russia, Ukraine, Belarus and other countries. That is, the most popular cartridge in the army, which is also called the “five”. Used for Kalashnikov assault rifles and machine guns of different series: Ak-74, Ak-74M, Ak-74MR, AKS, Ak-107, Ak-12, RPK-74, etc. Cartridges of this caliber can reliably hit an unprotected person at a distance of up to 1-1.5 km, and at a distance of up to 500-700 m they can penetrate light and medium-protective body armor. The advantages of these cartridges: there are a lot of them)), they are everywhere; a light weight, you can carry a lot; normal penetration ability at medium combat distance. Cons: the bullets of these cartridges are relatively light; when shooting in the forest at long distances, the bullets may deviate from the branches of the bush. Also, at short distances, when they hit a person’s unprotected body, they pierce it right through, which does not guarantee the quick death of the enemy, unless of course they mean a hit to the head.

4. Caliber 5.56x45 (NATO)

This is the main caliber of all American and NATO assault rifles and rifles. The number of types of these rifles is so great that there is no point in writing about them. It’s just important to remember: if our enemy is a NATO fighter or an American, we can say with a 95% guarantee that he will have a weapon of this caliber in his hands. This cartridge is slightly more powerful than our “five”, otherwise the parameters are virtually the same.

5. Caliber 7.62x39

This is the caliber of domestic weapons that were used during the USSR. But this caliber is also now extremely widespread in Arab and Latin American countries, as well as throughout the world (and here too) as cartridges for hunting weapons. The most common weapons chambered for this cartridge are:

Legendary Ak47, AKM and their modifications

Modern Ak-103, Ak-104 and Ak-12

Kalashnikov light machine guns

Civilian carbines Saiga and others.

Cartridges of this caliber have a very powerful shock-dynamic force: if in close combat you hit the enemy’s hand, it will most likely be torn off. Also, this cartridge can confidently penetrate any body armor and helmets in close combat. In case of war, having an Ak-103 + optics + a large supply of cartridges of this caliber in your hands is the height of dreams and aspirations.

6. Caliber 7.62x51

These are “killer” NATO cartridges. Most often used in sniper rifles, as well as in machine guns. This caliber is also used in our country, for example, in the new Ak-12 assault rifle, as well as in some machine guns. I am attaching a photo for comparison (from left to right) 7.62x51, 5.56x45 and a AA battery. The power of this caliber is very high, which is why it is used in NATO sniper weapons, and if you come under fire from a machine gun of this caliber, then... you understand.

IN different countries world, the caliber of a weapon is both designated and measured in different ways: either by the margins or by the bottom of the rifling of the barrel. In addition, the designation of the cartridge caliber can be conditional, for example, small-caliber cartridges. 222Remington and .22LR have almost the same caliber, but differ in type (the first cartridge is central ignition (capsule), the second is rimfire) and the size of the cartridge case.

So, in the countries of the former USSR, the caliber of rifled weapons is based on the distance between the opposite fields of the rifling, in NATO countries - by the distance between the bottom of the opposite rifling, the caliber of bullets (shells) is the largest diameter.

Rifled caliber small arms in countries that use the English system of measures (USA, UK, etc.), it is measured in fractions of an inch: in the USA - in hundredths (0.01 inches), in the UK - in thousandths (0.001 inches). IN general case, calibers are converted on the basis that 1 inch (1") is equal to 25.4 mm (2.54 cm).

In the inch system, calibers are designated in hundredths or thousandths of an inch, but without a leading zero, i.e. .50 caliber means 0.5 inches or 12.7mm, and .30 means 0.3 inches or 7.62mm.

In the recording, the zero of the integer part of the number and the designation of the unit of measurement (inch) are omitted, while in English-speaking countries a dot is used as a decimal separator: .45, .450 In Russian-language texts, traditional English and American calibers are written in exactly the same way, that is, with a dot, and not the comma adopted in Russia as a decimal separator: caliber 45 caliber 450, etc.; V colloquial speech: forty-five caliber, four hundred and fifty caliber.

In countries using metric system measures ( Russian Federation and all countries of the world except the USA, Great Britain, Myanmar and Liberia), the caliber is measured in millimeters, in its designation the length of the sleeve is added through the multiplication sign, for example 7.62 × 54 mm. It should be taken into account that the length of the cartridge case is not a characteristic of the caliber, but a characteristic of the cartridge. The cartridges can be the same caliber, but different lengths.

The following classification of small arms calibers is generally accepted:

Correspondence table for the most common calibers of rifled small arms

Shotgun caliber

For smoothbore guns, calibers are measured in a fundamentally different way: the number indicating the caliber is the number of round bullets for a particular gun that can be cast from 1 English pound of lead (453.5 g).

In this case, the bullets must be spherical, identical in mass and diameter, which is equal to the internal diameter of the barrel in its middle part.

The smaller the bore, the more bullets can be produced from a pound of lead. Thus, the tenth gauge is larger than the twentieth, and the sixteenth is smaller than the eighth.

Interesting questions sometimes arise during the writing and then discussion of materials about weapons. This happened after mine and the law enforcement officers. To be honest, it was somewhat unexpected for me.

An interesting conversation arose about the weapons that were used during the tests. More precisely, about the calibers of these weapons. The fact is that the data provided corresponded to the standards of the manufacturing countries. Which created some confusion in the perception of the material. Confusion caused precisely by poor knowledge of the very concept of “caliber”.

After some thought, I decided to make up for my mistake. Indeed, even those who professionally deal with small arms rarely think about the theoretical part. For what? There are our weapons, there are European ones, there are American ones. And this weapon is used with the appropriate cartridges. When using others, completely unnecessary delays and other troubles arise.

So, let's start with the basics.

Caliber is a numerical expression of the diameter of the bore, measured between opposing fields.

Everything seems to be clear. However, existing on this moment weapons do not always meet this definition. Why did this happen? The thing is that in the work of military personnel they use rifle. This circumstance makes the standard definition conditional.

For the most part, weapons meet the standard. But there are exceptions. Calibration by rifling is much less common. Simply put, the caliber is determined not by the field of the barrel, but from the depth of the rifling to the opposite depth of the rifling. But that's not all. Very rarely, but a third method of measuring caliber is also used. Along the rifling and field of the barrel opposite to each other.

So the questions that arose were quite correct. Although they arose during the use of weapons. Cartridges of the same caliber “do not fit” or “lobble” in the barrel. But more on that below.

Now about the designation of calibers in different countries.

Many have wondered about the famous Russian three-ruler. Why does this weapon have this particular name? Excellent rifle, 7.62 mm. Why three-line?

The caliber measurement system adopted in Tsarist Russia is to blame. 1 line corresponded to 2.54 mm. The attentive reader has already seen where the legs grow from. That's right, an English inch. 1″ = 25.4 mm. But since the calibers of small arms are still smaller, they were divided into lines. 1″ = 10 lines. And then simple arithmetic. 3 lines = 7.62 mm.

What I wrote above is a fairly well-known fact. But this fact has a continuation. When discussing the Mosin rifle, another name for the caliber was used: 30 points. Imagine: “the famous Russian thirty-point”... Indeed, this calibration system was also used at that time.
1 inch = 10 lines = 100 dots = 25.4 mm.

But let's return to our days. We're still more interested modern notation weapon calibers.

In most countries of the world, caliber is expressed in the notation we know. Millimeters. These can be either whole numbers or fractions. Fractional numbers are usually written to the second digit. 9 mm pistol and 5.45 mm machine gun. This entry gives more precise definition caliber.

But the UK and the US retained the caliber designation in inches. By the way, this also applies to other countries where the English system of measures has been preserved. Our “familiar” lines were also preserved, albeit in a slightly modified form.

In the UK, calibers are measured in thousandths of an inch. The Americans simplified the measurement a little. They make do in hundredths.

To fully understand this system, it is still necessary to return to our beautiful three-ruler. Officially, according to English requirements, the caliber of this weapon was recorded as 0.3 (3 lines = 3 x 2.54 mm).

IN English designation this caliber will be recorded as 0.300. In American - 0.30. The zero was removed for convenience, and today we have two remaining calibers: .30 and .300. But even this is most often not used today. You don't need a period either. Calibers today are simply designated 300 in the UK and 30 in the US. But for us this is the well-known 7.62 mm caliber.

30 (USA) = 300 (UK) = 7.62 mm (Russia).

This way it looks clearer. Now you, dear readers, can easily calculate the caliber of any weapon and convert it to a measurement system that is familiar to you.

We multiply the American caliber 30 by 0.254 mm and get our 7.62. We multiply the English caliber 300 by 0.0254 and get the same result.

By the way, I had one more question that tormented one of the readers. Why do Americans use a 5.6 mm rifle, and in Russian army 5.45mm automatic? In principle, I already gave the answer at the beginning of the article. And this answer lies in the caliber measurement technique. I’m not sure, but I think there was someone who wanted to dig into weapons and measure the bullet of our AK-74. Not when she's shot. And right in the cartridge. You will be surprised, but you were shooting with a 5.6 mm caliber. This is the diameter of the bullet itself.

The caliber of Russian weapons is measured according to a standard procedure. From field to opposite field. But if you measure the depth of the rifling, you get the desired 5.6 mm. But what I just described does not apply to all bullets. There are many factors that "reduce" the caliber of a bullet to the caliber of a weapon. And they even make this caliber smaller than the caliber of the weapon. This includes the amount of gunpowder in the ammunition, the hardness of the bullet, the number of rifling in the weapon, and the length of the leading part... The barrel of the weapon is not rubber. And the wear of such a barrel is an order of magnitude higher.

I didn’t want to “climb” into the wilds. But if the need arises, I’ll open this side a little. modern weapons, namely, cartridges. Today, the majority of small arms users (meaning rifled military weapon) are sure that the cartridge designation matches the caliber. And, alas, they are wrong.

The cartridge designation does not correspond to the caliber of the weapon. No, the calibers of the cartridge and the weapon are very close to each other, but do not completely coincide.

American police officers use 38-caliber revolvers. Using the method I described above, you can easily calculate this caliber in millimeters. 9.65 mm! But such a caliber does not exist in principle. And the cartridges used by the police are nothing more than ordinary 9mm cartridges! And such cartridges are used in weapons whose true caliber is only 8.83 mm.

And what is shown in Hollywood films, when a policeman takes out particularly powerful cartridges from a safe and proudly loads a drum with them, turns out to be, in the light of this article, complete nonsense. The “.38 Special” cartridges used in these revolvers are actually 357 caliber!

By the way, exactly the same thing is happening today with the Kalashnikov assault rifle, popular in the United States. Our cartridges and cartridges made in the USA, as they say, are two big differences. Both in terms of equipment and the caliber (true) of the bullet. But more about this some other time.

In general, the current system for designating weapon calibers is as simple as it is complex. Today it is impossible to count millimeters or inches in a primitive manner. Existing weapons even the same caliber has different receivers. The cartridges for most rifles and machine guns are “our own”. Unification, which was discussed quite recently, is becoming a thing of the past. Modern small arms are becoming highly specialized. The use of “foreign” cartridges can lead not only to weapon failure, but also to more dire consequences.

Interesting questions sometimes arise during the writing and then discussion of materials about weapons. This happened after my article about the standards of protection for military personnel and law enforcement officers. To be honest, it was somewhat unexpected for me.

An interesting conversation arose about which was used during the tests. More precisely, about the calibers of these weapons. The fact is that the data provided corresponded to the standards of the manufacturing countries. Which created some confusion in the perception of the material. Confusion caused precisely by poor knowledge of the very concept of “caliber”.

After some thought, I decided to make up for my mistake. Indeed, even those who professionally deal with small arms rarely think about the theoretical part. For what? There are our weapons, there are European ones, there are American ones. And this weapon is used with the appropriate cartridges. When using others, completely unnecessary delays and other troubles arise.

So, let's start with the basics. What is a caliber? Caliber is a numerical expression of the diameter of the bore, measured between opposing fields. Everything seems to be clear. However, currently existing weapons do not always meet this definition. Why did this happen? The thing is that military personnel use rifled weapons in their work. This circumstance makes the standard definition conditional.

For the most part, weapons meet the standard. But there are exceptions. Calibration by rifling is much less common. Simply put, the caliber is determined not by the field of the barrel, but from the depth of the rifling to the opposite depth of the rifling. But that's not all. Very rarely, but a third method of measuring caliber is also used. Along the rifling and field of the barrel opposite to each other.

So the questions that arose were quite correct. Although they arose during the use of weapons. Cartridges of the same caliber “do not fit” or “lobble” in the barrel. But more on that below.

Now about the designation of calibers in different countries.

Many have wondered about the famous Russian three-ruler. Why does this weapon have this particular name? Excellent rifle, 7.62 mm. Why three-line?

The caliber measurement system adopted in Tsarist Russia is to blame. 1 line corresponded to 2.54 mm. The attentive reader has already seen where the legs grow from. That's right, an English inch. 1" = 25.4 mm. But since the calibers of small arms are still smaller, they were divided into lines. 1" = 10 lines. And then simple arithmetic. 3 lines = 7.62 mm.

What I wrote above is a fairly well-known fact. But this fact has a continuation. When discussing the Mosin rifle, another name for the caliber was used: 30 points. Imagine: the “famous Russian thirty-point”... Indeed, this calibration system was also used at that time.
1 inch = 10 lines = 100 dots = 25.4 mm.

But let's return to our days. We are still more interested in modern designations of weapon calibers.

In most countries of the world, caliber is expressed in the notation we know. Millimeters. These can be either whole numbers or fractions. Fractional numbers are usually written to the second digit. 9 mm pistol and 5.45 mm machine gun. This notation gives a more accurate determination of caliber.

But the UK and the US retained the caliber designation in inches. By the way, this also applies to other countries where the English system of measures has been preserved. Our “familiar” lines were also preserved, albeit in a slightly modified form.

In the UK, calibers are measured in thousandths of an inch. The Americans simplified the measurement a little. They make do in hundredths.

To fully understand this system, it is still necessary to return to our beautiful three-ruler. Officially, according to English requirements, the caliber of this weapon was recorded as 0.3 (3 lines = 3 x 2.54 mm).

In English notation this caliber will be written as 0.300. In American - 0.30. The zero was removed for convenience, and today we have two remaining calibers: .30 and .300. But even this is most often not used today. You don't need a period either. Calibers today are simply designated 300 in the UK and 30 in the US. But for us this is the well-known 7.62 mm caliber.

30 (USA) = 300 (UK) = 7.62 mm (Russia).

This way it looks clearer. Now you, dear readers, can easily calculate the caliber of any weapon and convert it to a measurement system that is familiar to you.

We multiply the American caliber 30 by 0.254 mm and get our 7.62. We multiply the English caliber 300 by 0.0254 and get the same result.

By the way, I had one more question that tormented one of the readers. Why do Americans use a 5.6 mm rifle, while the Russian army uses a 5.45 mm assault rifle? In principle, I already gave the answer at the beginning of the article. And this answer lies in the caliber measurement technique. I’m not sure, but I think there was someone who wanted to dig into weapons and measure the bullet of our AK-74. Not when she's shot. And right in the cartridge. You will be surprised, but you were shooting with a 5.6 mm caliber. This is the diameter of the bullet itself.

The caliber of Russian weapons is measured according to a standard procedure. From field to opposite field. But if you measure the depth of the rifling, you get the desired 5.6 mm. But what I just described does not apply to all bullets. There are many factors that "reduce" the caliber of a bullet to the caliber of a weapon. And they even make this caliber smaller than the caliber of the weapon. This includes the amount of gunpowder in the ammunition, the hardness of the bullet, the number of rifling in the weapon, and the length of the leading part... The barrel of the weapon is not rubber. And the wear of such a barrel is an order of magnitude higher.

I didn’t want to “climb” into the wilds. But if the need arises, I’ll open up a little bit about this side of modern weapons, namely, cartridges. Today, most users of small arms (meaning rifled military weapons) are confident that the cartridge designation corresponds to the caliber. And, alas, they are wrong.

The cartridge designation corresponds to the caliber of the weapon. No, the calibers of the cartridge and the weapon are very close to each other, but do not completely coincide.

American police officers use 38-caliber revolvers. Using the method I described above, you can easily calculate this caliber in millimeters. 9.65 mm! But such a caliber does not exist in principle. And the cartridges used by the police are nothing more than ordinary 9mm cartridges! And such cartridges are used in weapons whose true caliber is only 8.83 mm.

And what is shown in Hollywood films, when a policeman takes out particularly powerful cartridges from a safe and proudly loads a drum with them, turns out to be, in the light of this article, complete nonsense. The ".38 Special" cartridges used in these revolvers are generally 357 caliber!

By the way, exactly the same thing is happening today with the Kalashnikov assault rifle, popular in the United States. Our cartridges and cartridges made in the USA, as they say, are two big differences. Both in terms of equipment and the caliber (true) of the bullet. But more about this some other time.

In general, the current system for designating weapon calibers is as simple as it is complex. Today it is impossible to count millimeters or inches in a primitive manner. Existing weapons, even of the same caliber, have different receivers. The cartridges for most rifles and machine guns are “our own”. Unification, which was discussed quite recently, is becoming a thing of the past. Modern small arms are becoming highly specialized. The use of “foreign” cartridges can lead not only to weapon failure, but also to more dire consequences.