Caliber?

Caliber is supposed to be the measurement of the diameter of the bore of a gun barrel in hundredths of an inch.

Despite the above definition of what caliber is supposed to mean, there are many guns whose manufacturer-designated and marked calibers don't measure up right. Most guns that are manufacturer-marked as 38 caliber are in reality more like 36 caliber by actual measurement. Many of the so-called 38 caliber guns, such as those chambered for the 38-40 cartridge are more like 40 caliber by actual meaurement. (The number 40 in the cartridge name is just the number of grains of black powder that the cartridge was originally designed to be loaded with. 38 is supposed to be its caliber, but it really isn't.) Many so-called 32 caliber guns are really more like 30 caliber by actual measurement. Most so-called 44 caliber guns are more like 43 caliber by actual measurement. There probably are several more examples we could mention where the manufacturer-marked calibers don't measure up right.

Whyisit that the manufacturer markings for caliber on so many guns and on so many cartridge headstamps fail to reflect what may be easily determined by actual measurement of the bore diameters?

Sam Heywood

One has to realize that a Barrel has two diameters. Bore Dia. which is the measurement between the lands. And Groove diameter which is the measurement from groove to groove. As an Industry standar. .30 Calibre has a bore diameter of .300' and a groove diameter of .308'. Do some research before you do any reloading and bullet casting and get all your ducks in a row before you end up in serious problems.

Good Luck. > ...

># of a gun barrel in hundredths of an inch.

>In practice, there are several possible meanings (apart from the >obvious one that millimetres are used as well as inches). The bullet >diameter may be used (slightly larger than the bore diameter) and in >addition, 'calibre' is sometimes used to describe a particular >chambering (e.g. '.50 Browning calibre MG' or in artillery, to >describe the length of the barrel (e.g. 45-calibre 155mm gun).

Usually when you see the word 'calibre' instead of the word 'caliber' used as a manufacturer marking, you are looking at a non-US made gun and the word is followed by a metric measurement. On a US made gun you often see the word written as 'caliber' followed by a metric measurement clearly indicated as such by 'mm'.

I have heard people using the word 'caliber' for referring to the length of a gun barrel in feet, but only in the context of naval artillery speak. I don't know if they speak of naval artillery in these terms in countries that use the metric system.

>[snip]

># Whyisit that the manufacturer markings for caliber on so many guns and >on ># so many cartridge headstamps fail to reflect what may be easily >determined ># by actual measurement of the bore diameters?

>The number used to describe the calibre may be chosen to distinguish a >cartridge for marketing reasons; for example, the .220, .221, .222, >..223, .224 and .225 all have the same .224 bullet diameter.

OK, but at least those designations are close and they are all within the acceptable range of plus or minus .005' of the accuracy implied by a measurement in hunredths, as in 22 caliber. The extra digit is not a meaurement to thousandths. It is just an extra digit used to distinguish one chambering or cartridge from another of the same diameter. What about 38 caliber? Most 38 caliber guns are actually .357 by actual measurement. Some, as in the case of the 38-40, are closer to 40 caliber. Now that ain't even close because it is far more off than just plus or minus .005'. Many 44 caliber cartridges and guns measure around .429'. That ain't close either.

>More examples of this at: >http://www.quarry.nildram.co.uk/ballistics.htm

Thanks for the URL.

Sam Heywood

Sam Heywood