Caliber names and designations have been causing confusion for probably as long as there have been caliber names. This is an easy thing to be confused by, so if you are bewildered, don't feel bad, you are in good company. New calibers are introduced every year whose names may or, just as likely, may not accurately describe their true size. If there is a general rule of thumb, the argument that seems to make the most sense is that cartridge designations usually are an indicator of bore size (the size of the hole drilled end-to-end through the barrel, before it is rifled), rather than bullet size (or, the size of the hole through the barrel at the widest point in the rifling).

Many caliber names are proprietary. In other words, they are used because they are at least close to being the correct designation of caliber, but more importantly for the maker, they sound cool and they fit the maker's theme. A name that sounds good, usually sells better than a name that sounds bad. Cool sounding names do not perform any better than drab, unexciting names.

Some caliber names from the last century such as 32/20, 32/40, 44/40, etc., are easy to decipher if you know how. The .44 in 44/40 refers to caliber, the /40 refers to the black powder charge weight. Oh yeah, but the bullet size of a 44/40 Winchester is really .427"; and that is closer to .43 caliber than to .44. So I wonder how popular the name forty two point seven/forty Winchester would have been? Right, 44/40 sounds much better, it has a classic ring to it, after all.

What they tried to do is give you a close idea of the caliber, which was really .43, but forty-four rolls off the tongue easier than forty-three does. Remember, too, that in 1873, the 44/40 was replacing a very popular cartridge for Winchester, the .44 Henry rimfire. In all likelihood they thought it important to keep that forty-four name in play, letting the public think it was an improved version of the successful Henry cartridge, rather than the entirely new animal it actually was. The 40 in 44/40 refers to the amount of black powder in grains weight avdp. that this cartridge actually did use, so this later part of the caliber description, at least, was accurate.

The percussion pistols bring to us more of the same. A .44 caliber Model 1860 Army fires a round ball of anywhere from .450" (.45 caliber) to .457" diameter (nearly .46 caliber) . The famous .36 Navy uses a .375-.380" round ball, making these .38 caliber. Why did they do this? The answers don't always make perfect sense, though sometimes there is a rational explanation if we fall back on that probable rule of thumb.

Let's look over a .44 cap-n-ball revolver. These use, for discussions sake, a .451" diameter bullet. That means the groove-to-groove diameter (rifling, bottom-to-bottom) is .451". But the bore diameter (rifling, top-to-top) has to be smaller than the groove diameter. So if the bored diameter of the hole in the barrel was .441" (.44 caliber), and we cut rifling grooves into the barrel which were .005" deep, the equation: .005"x 2=.010" (rifling total depth) + .441" (bore diameter)=.451" (groove/bullet diameter) would be true. So, yes, they called it a .44. Yes, the bullet is a .45, and yes, the barrel started out as a .44 before it was rifled, when part of it became a .45. Yes. . . just please don't say it too fast or we'll all get confused again!

Then we have those caliber names that were obviously applied for strategic reasons rather than pragmatic ones. Like .38 Special: this gun fires a .357-.358" diameter bullet, which is much closer to .36 caliber than it is to .38. The bore diameter is .350", which you can easily see is .35 caliber. Using our probable rule of thumb, it ought to be called the .35 Special. On the other hand, the .38 Special's elongated, pumped-up big brother, the .357 Magnum, is one of the most accurately described of all handgun cartridges. The .357 truly does fire a .357" diameter bullet, and at magnum velocities. Oops!

Some of these caliber names, at least as they apply to modern revolver cartridge names like the .38 came, I believe, from the early days of cartridges, when a great many cap-n-ball revolvers were converted to rimfire and center-fire cartridge use during the years following the Civil War. In order to make the new cartridge shoot accurately in these guns, the bullets had to be of a correct size to fit the pistols rifling. In the case of a .36 Navy, this cartridge would have held a true.38 caliber bullet. I think the .38 part just stuck because its a popular name that sounds good. Thirty eight also sounds like its bigger than .36, which implies that it may be more powerful.

Some calibers from the same era were more accurately identified by their monikers. The .44 S&W American, and the .44 Henry Rimfire both had barrels which measured .439"-.440" groove-to- groove. These were really .44s. The venerable .45 Colt is also a true .45 caliber in bullet diameter. The 45/70 Government used .457-.458" bullets, much closer to .46 caliber than .45, but the bore diameter was .449", or .45 caliber.

The .45/70 was originally a military cartridge, the /70 designating the weight of the black powder charge, not the year of adoption. The U.S. military has, as a rule, applied the bored size of the barrel hole to the caliber designation. The 30/06, for example, uses .308" diameter bullets, yet the barrel's bore size is .300", or exactly .30 caliber. The /06 in this caliber designation is not a powder weight indicator in this case. Unlike the 45/70, the identifier at the end of its name means that this .30 caliber cartridge was adopted in the year 1906.

What about those metrics that use only a bunch of numbers and exes? European manufacturers have pulled some of the same nonsense, although generally the metric designation will be a fairly accurate description of the cartridge. For instance, a 9.3 x 74R designation means that this gun fires a 9.3mm diameter bullet from a cartridge case that is 74mm in length. The R denotes a rimmed cartridge case. In Europe, many standard rimless cartridges were altered to a rimmed configuration for use in drillings and double rifles. The rim allows easy extraction with the simple, lifter type extractors that are used in these weapons. The classification 7 x 57mmR Mauser is a good example of the standard 7 x 57mm Mauser round that has been manufactured with a rim for these purposes. Some American cartridges that are popular in Europe have been given their own metric names, like the .22 Hornet, which becomes the 5.6 x 35Rmm in its continental alias. Our American designed metrics often aren't that well described, usually containing only the bullet size followed by the proprietary maker's name. The 7mm Remington Magnum is a good example of this naming practice.

All of this only means that we shouldn't jump to any snap judgments about what a given caliber may be, at least not based solely on the indications in its given name. Don't get confused by what appear to be the facts in this name game, do your homework! For a great read and an invaluable resource on this topic, get yourself a copy of Cartridges of the World, published by Krause Publications, 700 East State St., Dept. BNP, Iola, WI 54990, (800) 258-0929.