| Writers often need to know just what kind of | | | | inches in diameter. A .38 Special isnot .38 inches. It |
| weaponry their protagonists are using. Here's a | | | | is .357 inches. The .357 Magnum, though, is truly |
| useful primer as to the different terms and what | | | | .357 inches in diameter. A 9mm is .355 inches. |
| they mean. | | | | Some calibers are alsoconfusing. A .45 Colt is a |
| CALIBER (or calibre) is "usually" a numerical term, | | | | revolver cartridge. A .45 ACP (Automatic |
| without thedecimal point, in a cartridge's name to | | | | Colt Pistol) is an automatic cartridge. They are not |
| indicate the bullet diameter. | | | | interchangeable. |
| Alternatively it can be a measurement of the | | | | Caliber also has an alternative meaning when it |
| diameter of the gun'sbarrel. | | | | relates to the lengthof the barrel in larger, artillery, |
| It is described in most glossaries as: "The internal | | | | pieces eg an artillery piece maybe described as 5 |
| diameter of agun's barrel." This can be measured | | | | inch/50 caliber, which would mean it has a barrel |
| either in English units or inmetric. The | | | | 50 times the bore diameter, or 250 inches long. |
| measurement can be taken in a rifled arm either | | | | GAUGE refers to shotguns and is the bore size of |
| land toland or groove to groove. E.g., in most US | | | | a shotgun determinedby the number of round |
| .30-caliber rifles, thediameter of the bore land to | | | | lead balls of bore diameter that equals a pound |
| land is .300 inches, while groove togroove it is .308 | | | | For example, twelve lead balls that fit the |
| inches ( Land is the raised portion of rifling inthe | | | | diameter of a 12 gaugeshotgun equal one pound. |
| barrel, groove is the recessed portion of rifling) | | | | The most common sizes of shotgun gauge are |
| In the US the measurement is usually expressed | | | | 10gauge, 12 gauge, 16 gauge, 20 gauge, and .410. |
| in hundreds of an inch;in Great Britain in | | | | ( Again, just toconfuse matters, the .410 is the |
| thousandths; in Europe and elsewhere inmillimetres. | | | | exception in shotguns in that it ismeasured as a |
| That's why you see the calibre of handguns | | | | caliber not a gauge, so the .410 has a barrel |
| oftenexpressed in different units. | | | | .410inches in width.) |
| Just to confuse matters, even in the same | | | | So, using this system, as the gauge goes up, the |
| country the quoted calibredoes not always | | | | bore diameter goesdown. This is the opposite of |
| indicate the true bore diameter but measure | | | | calibre. Just remember, as a writer, your duty is |
| thediameter of the "outer" barrel. | | | | to get it right. And also remember, there's always |
| Not all calibers indicate bore diameter. The .44 | | | | going to be somebody out there who'll point out |
| Magnum is not .44inches in diameter. It is .429 | | | | your mistakes, so try to get it right first time. |