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What "relationship"?[edit]

The first sentence:

...diameter of the barrel in relation to the diameter of the projectile...

makes it sound like caliber is a ratio or difference between two diameters. But it's really an absolute number. Would it be more correct to say:

...diameter of the barrel or the projectile...

im here to tell u dat is not correct  — Preceding unsigned comment added by (talk) 14:10, 17 September 2013 (UTC) 


The main Caliber#Firearms section of the article is way over-simplified. I intend to merge in something like:

Traditionally calibres were expressed in inches, and this is still the norm for civilian firearm calibres of US origin. However, due the the long period over which this system was used, it accumulated many complications which mean that a calibre in inches is often not simply, or not even, the same as the actual diameter of the lands. Some have suffixes with largely arbitrary meaning. For example, in the .45-70, the .45 refers to the calibre while the 70 refers to the charge of black powder (in grains) with which it was originally loaded; similarly the .30-30 had a .30" diameter and took 30 grains--but of cordite this time. And the .30-06 didn't take 6 grains, it was type approved (adopted by the U.S. Army in 1906)! Even more complicated, sometimes the "suffix" is encoded into the calibre itself, even to the extent of making it wrong. Thus the .22 WMR, .218 Bee, .22 Hornet and .223 are all actually the same diameter (which is .224", not .22"!) with the numbers varied to indicate that other aspects of these cartridges make them non-interchangeable. Even more extremely, the .38 Short, .38 Long, and .38 Special are all the same diameter, and it isn't .38", it's .357", the same as the .357 Magnum; in fact each of the smaller cartridges in this series can be safely fired in chambers meant for larger ones, but not the other way around.
With this kind of historical confusion, fortunately metric calibres are much simpler. The calibre in millimetres is simply the true diameter of the lands (or, occasionally, the bullet; we wouldn't want this too simple!), to some reasonable tolerance. If this leaves ambiguity it is clarified by following with the length of the cartridge case in millimetres. Thus we have the 7.62 x 51 mm (a NATO standard) and the 7.62 x 39 mm (a Warsaw Pact standard). Metric calibres are used for practically all military calibres (including post WW2 US ones) and most civilian calibres originating outside the US, at least recently.

But someone might like to fact check it first! Securiger 17:12, 14 Mar 2005 (UTC)

So instead of over-simplified we risk over-complicated? GraemeLeggett 09:05, 15 Mar 2005 (UTC)

"9 mm" might very well be the only metric measurement many Americans know of. JIP | Talk 10:20, 6 May 2005 (UTC)

I very much object to the article's claim that "It is technically incorrect to say 9 mm cal.". The subsequent paragraph clearly and correctly states that caliber is not a unit of measurement, so why isn't "9 mm cal." (or "9 mm caliber") fine? Woseph 11:37, 28 May 2005 (UTC)

  • After three months of no comments or changes, I'm removing the offending sentences from the article. -- Woseph 07:36:09, 2005-08-31 (UTC)

Conventions of measurement in firearms[edit]

The author of the article, "Caliber", gives one convention for bore measurement - that is the minimum or nominal diameter measured in a barrel's bore. In a rifled barrel bore, there are two diameter dimensions - commonly referred to as groove diameter and the other nominal diameter.

Groove diameter is the maximum dimension of a bore between the bottoms of the grooves of the rifling. In direct measurement terms, this is often only intrinsic since two maximum points of groove depth may not exist because the rifling's geometry may not pose two such points in diametric opposition in the bore. Still, when a slug is upset and pushed through the bore and measured for maximum obturated diameter, it will yield "groove diameter".

Nominal diameter is the diameter of the theoretical cylinder measured at two points on the surface of the rifling's lands. The nominal bore diameter, then, is the groove diameter less twice the land height (or groove depth).

Rifled barrel manufacture takes place in one of two ways and the confusing conventions as to bore measurement arise from this.

In one means of manufacture, a mandrel bearing the dimensions of the rifling as raised ribs on a cylindrical bar in a helical pattern (the measure of the helix pitch being the "twist" or "rate" of the rifling, generally expressed as a ratio of one full turn of the helix in a given number of inches)is inserted in a tube of approximate groove diameter internally. The tube is then upset onto the mandrel, forcing the mandrel's profile into the tube. The mandrel is withdrawn and the tube is now a rifled barrel having a groove dimension more or less as the tube began and a nominal dimension more or less that of the mandrel cylinder. Commonly, this means of rifling is referred to as "hammer forging" for the impact process of hammering the tube into upset on the mandrel. This is the earliest form of rifled barrel manufacture and dates to the time when all barrels (and all tubes, for that matter)were formed by the "Damascus" process of hammer and forge welding of strips of "steel" together to form a tube around a mandrel.

In the other means of rifling, a tool is passed through a tube of nominal diameter to either cut or upset the rifling pattern into the bore. The variety of techniques to accomplish this method is great enough to be beyond the scope of this addendum.

Bottom line, both measures are diameter, rifled barrels have two "bore" diameters, and any consistency in their general reference naming is coincidental.

Respectfully submitted,


US vs British[edit]

Folks, why all the refs to "calibre" are now replaced with "caliber"? Does it mean that americal english (Mein Gott! I found this sequence of words real fun!) is now the language standard for the whole world? /BTW, the xUSSR was using british english as educational standard.../ --jno 07:53, 19 June 2006 (UTC)

Its for consistency within the article. If an article starts off with US English spelling then it is the done thing to stick with that no matter what the author's natural usage is assuming that the article is not of itself naturall BE or AE - see the MoS for more details GraemeLeggett 08:40, 19 June 2006 (UTC)
I mean another articles, like 7.62 mm caliber. --jno 11:23, 19 June 2006 (UTC)


Can anyone explain the origins of some of the calibers? Why, for example, is there a .22 caliber, a .357, a 7.62mm, and so on? Why did someone decide to manufacture the ammunition in these weird numbers instead of round figures?

Septegram 20:41, 24 August 2006 (UTC)

Some countries still use inches, while others have switched to SI (metric).
And now we have (7.62 mm ÷ 24.5 mm/inch ≈ .311 inch)
Then take into account that, say, a "SI based country" has purchased the license to build an ammo from "inch based country" and converts the documentation...
Add the different ideas of measuring "caliber" as internal diameter...
Moreover, read carefully for the info of "mere caliber numbers" obtained as a number of spherical bullets made of 1 pount of led... --jno 10:46, 28 August 2006 (UTC)
OK, I can see how the metric numbers are odd because they're conversions from equally-odd non-metric versions, but who on earth decided to make bullets at .311 inches diameter? Were they all based on fractions of a pound of lead?
Thanks for your help, by the way. This is something that has always baffled me. I'll go back and reread the sections you mention when I have a minute or six.
Septegram 14:56, 28 August 2006 (UTC)
Anyway, it's mostly historical issues with those "odd" caliber numbers, and the "number of spheric bullets of 1 pound of led" seem to be the simplest reason :-)
Take into account, that cartrige production is "more basic" than firearms for that cartriges! There are lots of firearms made for an existing cartriges (even for non-domestic! Fedorov's automatic rifle for captured japanese ammo, for instance), but new ammo get introduced very rare. --jno 09:05, 31 August 2006 (UTC)
This is kind of related to septegram's question, but can someone provide a list of the most common calibers, and possibly their mm equivalents? It'd be helpful for gun-ignorant people such as myself. Ailes Grises 22:21, 22 April 2007 (UTC)
A couple of comments. First, people experiment with different sizes for various reasons. They're more concerned with making a round well suited to a particular purpose than they are to having a round number. Second, the naming conventions often don't match the actual size, they're more of a marketing decision. Third, different countries use different measurements, for example the US typically uses bore size, while the UK uses groove size. For a complete list of popular calibers, there is one in the subscriber section at if you're a member there. For a list that's still being worked on, see Table of pistol and rifle cartridges by year which is unfortunately sorted by year, not by size, but tends to show measurements in metric and in inch. I added a VERY SHORT list to the article, Note that everything is rounded for simplicity. It's just the basic rifle stuff, .17 (4.4mm) up to .30 (7.62mm) Arthurrh 18:50, 1 August 2007 (UTC)

"Decimal is dropped when spoken"[edit]

The article says that the decimal point is ignored when someone says it, so that a 0.22 inch barrel is called "twenty two calibre". What do you call a cannon with a 22 inch barrel? I don't think this stupid suggestion of ignoring the decimal point should be included in an encyclopaedia. Whoever wrote it has a severe lack of common sense and they were wrong to say that the decimal point "is" ignored, since it is really just a suggestion. Huey45 03:39, 5 August 2007 (UTC)

Well I've never heard anyone anywhere ever call a 22 caliber a .22 caliber. It's just not what's done. By the way, a gun with a 22 inch diameter barrel would NOT be a 22 caliber, it'd be a 22 inch gun. It's not correct to say "1 caliber = 1 inch". Arthurrh 04:10, 5 August 2007 (UTC)
Saying "Point Twenty-Two" is considered to be a very n00b-like thing to do amongst every shooter I've ever spoken to; it's what people who are new to shooting (or learnt everything from books without any real practical experience) say. You'll notice knowledgeable shooters don't refer to a "Point Thirty-Oh Six" or a "Point Three-Oh-Three" or a "Point Two Two Three"- the "point" is only spoken when it's referring to a decimal calibre, such as "Seven Point Six Two by Fifty-One NATO", "Five Point Five Six", "Six Point Five by Fifty-Five Swedish", and so on. --Commander Zulu 10:53, 5 August 2007 (UTC)
In the UK a .22 calibre round is called a two-two, a .410 shotgun cartridge a four-ten, and a .303 a three-oh-three. Metric ammunition is usually the same, e.g., 7.62mm a seven-point-six-two. Confusingly, what the US calls a 12 Gauge is referred-to as a twelve-bore. For airguns a .177 is just a one-seven-seven. Generally, if you hear someone in the UK using the US terms you know that their knowledge of firearms is confined to what they've heard in American cop shows on the TV. —Preceding unsigned comment added by (talk) 21:27, 16 May 2009 (UTC)
I notice that the "twenty two calibre" has been replaced with "two two calibre". I have never heard this notation. In Australia we say "twenty two calibre". We also say "three-oh-three" though so maybe it's a mix. (talk) 05:07, 13 June 2009 (UTC)
Neither have I; at least not from anyone who actually shoots. Perhaps it should be changed back? Commander Zulu (talk) 05:24, 13 June 2009 (UTC)
Speaking the decimal in an inch caliber as "point" just isn't done in the US, unless you are into handloading your own ammo and are trying to order bullets over the phone - from Maine :). From comments here appearing to originate in Commonwealth countries, it seems that they do not speak the "point" designation either. To complicate matters further, many people in Southern and Western US States speak metric calibers without the decimal, e.g. "seven six two" is a common slang term for 7.62x51mm NATO, and "five five six" is common for 5.56x45mm NATO. This is catching on in many other places as the web brings video and the spoken word to the world, not to mention worldwide TV syndication of US cop shows ;). Also the US in general uses the processional(?) names when speaking a caliber, such as "twenty two, thirty eight, forty five" versus "two two, three eight, four five". There are exceptions here too, such as the oddly intermixed, yet popular phrase "three fifty seven" for the .357 Magnum caliber. (talk) 18:46, 1 January 2010 (UTC)


QUESTION: The first sentence of the section titled "Firearms" refers to "the radius of the bullet used." Throughout the article, caliber refers to a diameter, of the barrel or the projectile. Which is it? It seems to me that the radius is not used/ —Preceding unsigned comment added by (talk) 15:35, 17 November 2008 (UTC)

It is the diameter, and I have fixed that sentence. scot (talk) 15:43, 17 November 2008 (UTC)


Could someone add information on 14.5mm Heavy Machine Gun and sniper rounds? —Preceding unsigned comment added by (talk) 03:07, 28 December 2008 (UTC)

  • I was curious about that. I considered fixing that but I was wondering if it was left off for a certain reason. Does anyone know if it was purposefully excluded? Noha307 (talk) 00:34, 22 July 2010 (UTC)
The article is about the definition of calibre and includes a list of "some" rounds with conversions. The list could probably be trimmed further. GraemeLeggett (talk) 08:42, 22 July 2010 (UTC)

Grammatical position[edit]

Which is correct, Caliber .22 or .22 caliber? --THE FOUNDERS INTENT PRAISE 19:53, 21 January 2009 (UTC)

".22 caliber" is by far the more common usage, although I have seen the form "caliber .22" used, primarily from British sources as I recall. scot (talk) 21:10, 21 January 2009 (UTC)

Naval guns and Calibres[edit]

Someone needs to look up a specific and authorative reference for the meaning of the word "calibre" in American naval language. It is also justified as being the worldwide standard in the English language, because ever since about 1 January 1943, the U.S. Navy has been continuously the world's largest and best-armed one.
In the massive work, "History of United States Naval Operations in World War II" by lead author Samuel Eliot Morison and his team of researchers and other colleagues, Morison clearly explains what "calibre" means on warships. It is the length-to-bore ratio of a naval gun. To give you a couple of examples, a 5-inch 54-calibre naval gun has a barrel (5" x 54) = 270 inches long, which is 22 feet and six inches long. This type of weapon has been used on a large number of American and foreign warships, including destroyers, guided-missile cruisers, nuclear-powered cruisers, and amphibious warefare ships. The prominent ones in U.S. Navy service now are a large number of USS Arleigh Burke-class guided-missile destroyers - the older ones - and the USS Ticonderoga-class guided-missile cruisers, as their gun armament, with one of these on each destroyer and two on each cruiser.
Another example is with the single naval gun that is mounted on 25+ of the newer USS Arleigh Burke-class destroyers, which is a 5-inch 62-calibre naval gun. It has a barrel (5" x 62) = 310 inches long, which is 25 feet and ten inches long.

I think that the present article on "caliber" is impossibly confusing between the words "caliber" and "calibre". There needs to be a separate article on the calibre as defined for naval guns. [I have even seen such absurdities in other Wikipedia articles as such a piece of naval artillery being described as 5-inch (62 mm). I am not joking!]

Furthermore, some people here have complained about weapons ammunitions with diameters of a strange assortment of nice, round numbers in the metric system, and strange numbers that are actually conversions from the American / British system of units. Well, what they are neglecting to observed that a certain set of standard ammunition diameters was chosen as NATO standards so that one large inventory of ammunition could be used by e.g. 15 different countries. Also, the U.S. Army and Marine Corps has long used a lot of standard metric system diameters for their weapons, and beginning during WW II, the U.S. Navy adopted a lot of metric sizes, also. When the U.S. Air Force became a separate service in late 1947, it soon began to adopt more and more metric system-sized ammunitions.
The NATO & U.S. Army standard ammunition diamters included 20 mm, 25 mm, 30 mm, 40 mm, 75 mm, 81 mm (mortar rounds), 90 mm, 105 mm, 120 mm, 155 mm, and 175 mm, plus just the standard 9.0 mm pistol round that they U.S. Armed Forces were rather slow to adopt.
Furthermore, based on American weapons in American units, there came the 5.56 mm rifle ammunition, based on the American M-16 rifle which originally fired a bullet of about .223 caliber; also the 7.62 mm bullet, which corresponds to about .30 caliber; and a big six-inch artillery piece that corresponds to something like 203 mm - they used to be in West Germany to threaten to fire nuclear shells, and thank God it never, ever came down to that; and the 12.7 mm machine gun bullet, which is based on the celebrated American M-60 .50 caliber machine gun. The .50 caliber machine gun has been in American service for a long, long time, and it traces its roots to a Browning .50 caliber machine gun - one that I believe was designed by an Englishman, but which first went into large-scale production production in the United States. Besides its massive service with the American infantry, armor, and Marine Corps during WW II, the .50 caliber machine gun went into huge service with the Air Services of the U.S. Army, Navy, and Marine Corps during WW II. Let me name some of the warplanes that carried between four and ten of these machine guns during WW II: B-17 "Flying Fortress", B-24 "Liberator", B-25 "Mitchell", B-26 "Marauder", B-29 "Superfortress", F4F "Wildcat", F6F "Hellcat", P-38 "Lightning", P-40 "Warhawk", "P-47" Thunderbolt (eight of them one one fighter plane!), P-51 "Mustang", PB4Y "Privateer" (the Navy's version of the Liberator, used by the thousands). Then along came the Korean War, and jets, and there were the .50 caliber machine gun armed F-80 "Shooting Star" and the great F-86 "Sabre" (six .50 caliber machine guns on most models)
Also, during WW II, the Navy bought licences to manufacture 20 mm anti-aircraft guns from the Swiss, and 40 mm anti-aircrft guns from the Swedes. American factories made these by the tens of thousands - and I hope that the Swiss and Swedes were paid well - because they were superb anti-aircraft defensive weapons for ships of all kinds. Also, besides their four machine guns, all P-38s got one 20 mm rapid-fire cannon, and I believe that most Navy/Marine F-4U Corsairs had six of these 20 mm cannons. The B-29s also carried several of them. There was a model of the F-86 that had four of them, rather than machine guns.
In any case, the air warriors were moving into larger, harder-hitting weapons during the Cold War, and either the 20 mm cannon or the incredible 20 mm Gatling gun became very widespread. (They cut up enemy warplanes like chainsaws.) I'll name some widely-produced American warplanes of the jet age that have carried 20 mm guns: F-100, F-101, F-104, F-105, F-111, F-4 "Phantom II" (most of them that were produced - and also carried in external pods - and flown by the Navy, Marines, and Air Force), F-8U, F-14, F-15, F-18, F-22, A-7 "Corsair II" (flown by the Navy, Marines, and Air Force), B-52, B-57, and AC-130. I'll let you hunt for more, if interested. So, those who claim that Americans don't make and use metric ammunition and guns are somewhat cockeyed. The A-10 "Thunderbolt II" "tank buster" was built around a huge 30 mm rapid-fire anti-tank gun, and the British-designed, but American-modified AV-8B "Harrier" carries regular 30 mm rapid-fire cannon. (I was working at McDonnell Douglas when a completely-different division was developing the AV-8B from the British AV-8A. Among other things, the AV-8B got a completely-new set of wings, made with the brand-new carbon-composite materials. They are larger for more lift, but weigh less, which you always want for an airplane. Besides being flown by our Marines, the Spanish Navy and the Italian Navy have them, too. Did we sell any back to the British? I don't know.)
As for the AC-130 "Specter", besides its 20 mm cannon, it has some 40 mm cannon, plus a 105 mm howitzer that fires right out the airplane's tail door. It's not nice to mess with an AC- (talk) 07:20, 2 December 2009 (UTC)

1. 203mm is a 8 inch howitzer, not 6 inches. These cannons left the US inventory in the 90s. 2. F4U Corsairs never had 6 x 20mm cannons. They either had 6 x .50 cal M2s or 4 x 20mm (later variants). 3. The 30mm GAU-8 in the A-10 is a Gatling-type weapon, just like it's counterparts in other aircraft (20mm in the fighters) the M61 Vulcan, and the 7.62x51 GE M134 "Minigun" used on ground, waterborne and often helicopters.Caisson 06 (talk) 03:28, 9 October 2013 (UTC)
A) The "American M-60" machine gun you refer to is chambered in the standard 7.62x54 NATO caliber, not .50 caliber as you state. You are thinking of the M-2 and it's heavy barreled brother the M-2HB, also known in American military parlance as the "Ma Duce". The M-2 is chambered in the .50 Browning Machine Gun (or .50 BMG for short) caliber. B) John Moses Browning was a United States born firearms designer and genius in firearms engineering who invented many of the innovations you still see today on modern rifles, pistols, and shotguns. He was *not* an Englishman. (talk) 19:14, 1 January 2010 (UTC)
NATO standard is 7.62 x 51mm. 7.62 x 54 is the old Russian rimmed round used on everything from old Nagants to SVD (Dragunov) sniper rifles.Caisson 06 (talk) 03:28, 9 October 2013 (UTC)

Multiple subjects, splitting[edit]

Caliber seems to suffer from trying to be a dictionary definition, dabbling in many meanings, as well as covering multiple bona fide encyclopedia subjects. At the least, I think the artillery subject should be split off from the firearms subject. I may undertake to do this, if I'm up for it. Thoughts? ENeville (talk) 16:19, 10 February 2010 (UTC)

I think it's a good idea. Firearms and artillery weapons are completely different weapon systems so I think it would be wise to split the caliber article into two articles, one dedicated for the definition for firearms and one for artillery. It can help avoid confusion on articles like 5"/38 caliber gun. I had to carefully look at the caliber article twice to assure the correctness of information in the gun article.--Fogeltje (talk) 23:00, 10 February 2010 (UTC)

A problem in the very first sentence. " relation..." (HUH???)[edit]

The first sentence as it currently reads is this:

In guns including firearms, caliber or calibre is the approximate internal diameter of the barrel in relation to the diameter of the projectile used in it.

This is in error. The quantifier is that of a diametric measurement. Not of a diameter in relation to another diameter. Unless you intend to say that Caliber is itself a relationship of two diameters (it is not), then this needs to rewritten. If caliber has multiple meanings (say bullet vs. casing vs. barrel diameters), then say so. But it is NOT something "in relation" to something else. Tgm1024 (talk) 03:14, 31 December 2011 (UTC)

.44 Magnum ?[edit]

May be a silly question, but I don't see the .44 magnum in this page. and there is no .44 diameter line in the table. Is this intentional?

Not silly, but there is simply no need or room to include an exhaustive list of every caliber in existence. Jason Kilgore 20:41, 5 January 2015 (UTC) — Preceding unsigned comment added by Jwkilgore (talkcontribs)
I went ahead and added it. Ghostofnemo (talk) 07:24, 6 January 2015 (UTC)

Caliber as a unit[edit]

Is there an article which gives the clear statement that 1 caliber = 0.01 inch? I can see that the situation is complex (and in some contexts, "caliber" can refer to length/bore), but surely the definition should be stated somewhere? I am wondering what should be done with Calibre (unit), a new article at AfD. Should it be a redirect to here? Clearly this article is about guns, but since its title is "caliber" it should cover basic encyclopedic information, such as its definition. Johnuniq (talk) 10:06, 21 December 2014 (UTC)

Expanded definition in lead to address your concern - "usually shown millimeters, or in hundredths or thousandths of an inch. When expressed in inches in writing or print, it is shown in terms of a decimal fraction: .45 caliber, for example." Ghostofnemo (talk) 07:31, 6 January 2015 (UTC)
Except when it isn't? eg "Rifle, Anti-Tank, .55in, Boys". GraemeLeggett (talk) 12:07, 6 January 2015 (UTC)

Caliber doesn't only apply to self-contained cartridges.[edit]

The article discusses "caliber" as generic bore diameter, but many statements appear to only apply to rifled small-arms weapons firing modern self-contained cartridges. For example:

"Firearm calibers outside the range of .17 to .50 (4.5 to 12.7 mm) exist, but are rarely encountered." -- Completely not true, because shotguns are considered firearms and can go considerably larger (rifled barrels on the very common 12-gauge are .73"), and .52" Caliber muzzle-loaders are readily available. This statement really doesn't belong in an article about "caliber", unless it is moved to a new section specific to rifled small-arms weapons firing modern self-contained cartridges.
"The .950 JDJ is the only known cartridge beyond .79 caliber used in a rifle." -- Depends on your definition of "rifle", it ignores the huge number of larger-diameter rifled military guns, and ignores much larger shoulder-fired and mounted shotguns. With a weapon weight of 85-lb+ and with 200-ft-lbs of recoil energy, it's not like a .950 JDJ can be realistically shoulder-fired, so how is it different from a larger-diameter 37mm M3 Anti-tank gun? Actually, the whole paragraph containing this and the previous quote should be moved to a new section. Jason Kilgore 20:37, 5 January 2015 (UTC) — Preceding unsigned comment added by Jwkilgore (talkcontribs)