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Calibre?


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I hope this is the correct forum for this post.

What do the numbers after a weapon's (usually a rifle/pistol) name mean? e.g AK-47 7.62 x 54

I have been looking all over the net for this info all morning and can't find it anywhere.

cheers,

delboy

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There's no real universal standard for cartridge designation.

In America in the 19th century, there would be two numbers, the caliber and the amount of blackpowder in the case, in grains. so a 45-70 was a .45 caliber bullet with 70 grains of blackpowder. The latter number became nonsense with the advent of smokeless powder.

Then the US military started using a caliber-year of adoption format, the most famous being the 30-'06 (.30 caliber, adopted in 1906).

The caliber x length convention was a European one that the Americans finally adopted after the establishment of NATO.

Commercial cartridges have completely different conventions. Sometimes, as with the 38 Special, the number doesn't even refer to an actual caliber, and was designated as such for marketing purposes.

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".50" refers to a bullet diameter of .5 inches (12.76 millimeters), usually the .50 Browning Machine Gun catridge.

Gauge, used for measuring shotgun bores, is more complicated. It is measured (historicallly) by pouring a given amount of shot into a tube and seeing how high it piles up. In a narrow tube, the shot will form a high column, and in a wide tube the shot will form a low column. The height of the column (which relates inversely to the cross-sectional area of the bore) determines the gauge. Thus, the higher the number, the wider the bore; a 20 gauge barrel has half the interior volume of a 10 gauge barrel of the same length. The relation between diameters and gauges involves pi and I'm feeling too lazy right now to work it out. I do know that a 12 gauge is about .72 caliber.

As a general rule, caliber designations are misleading because they involve a complicated history of a cartridge design such as what cartrides a round was adapted from, what year is came out, what length its case is...... For instance, while the 30-06 refers to a .30 cartridge adopted in 1906, the 7mm-08 refers to a 7mm cartridge necked down from a .308, also known as the 7.62x51mm, not to be confused with the 7.62x39 (AK), the 7.62x54R (SVD), or the 7.62x25 (submachinegun), all of which can be called 7.62 russian. Yeah.

BTW, the 9mm(Luger, short, makarov), .38 (special, long, auto) and 357 magnum all have the exact same bullet diameter, .356 inches. The .38 special was so called to bank on the popularity of an older cartridge which actually was .38 inches across.

Edited by mob
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