by Hap Rocketto
I am sure that you are like many people who notice when little technical things in stories, or movies, are not quite right. If you are a SCUBA diver you might notice that the character is wearing the wrong type of regulator. If you like airplanes an interior that does not match up with an exterior view might jar you, and as shooters we all seem to notice the lack of recoil in cannons or rifles. In print the one thing that really drives me around the bend is the simultaneous use of the decimal point and term caliber to describe the size of a firearm.
If a number is written .22 it is read as “twenty two caliber” or it can also be correctly written as 22 caliber. But when written with both the decimal point and the word, i.e. .22 caliber, it is correctly read as “twenty two one hundredths caliber”. The decimal and the word, when used together, are either redundant or misleading. The most common definition of the word means the diameter of the bore. A caliber is an English unit of measurement equal to one one hundredths of an inch. The only correct way to write it is either as a number with a decimal, .22, or in its entirety as twenty-two caliber. It should be easy enough to do correctly but even the pros seem to make the mistake.
Caliber is an old word. In fact the Greeks, as the saying goes, had a word for it. Greek sports writers did not have the problem of the multiple use of the decimal point and the word that we have today. But in the days of ancient Greece it was a lot harder to get into print the wrong way. In the first place there was no print. Back around the time of Archimedes the Greek’s who ‘rolled their own’ ammunition had to deal with this formula to define the caliber of a catapult. I found the definition in James Adams’s splendid little book on engineering entitled Flying Buttresses, Entropy, and O-Rings.
“Multiply by 100 the weight-in minas-of the stone missiles. Take the cube root of the product and add 1/10th of the number thus produced. This gives the caliber in daktyls.” For your information a Greek dactyl was approximately 3/4 inch, or 19.0 mm. The minas was just under a pound, or 436 grams. And to think we believe we have a hard time when we have to convert calibers to millimeters.
A second, and less well known shooting definition of the word, other than the earlier stated diameter of the bore measured from opposing lands, is a measurement of the ratio of barrel length in to bore diameter. For example, the most common United States naval dual-purpose gun of World War II, the 5-inch/38 caliber, had a barrel length equal to the product of 5 and 38 or 15 feet 10 inches. This definition of caliber is also used to measure the relative effectiveness of artillery pieces. Given a situation where the diameter and other characteristics of the shell are the same the longer the barrel the more potent the gun.
I’ll illustrate some of the problems the Hellenic handloader may have faced by using the most common Greek field artillery piece during World War I, the 70 mm 17 caliber Schneider-Danglis Field Gun Model ’08. The ’08’s shell tips the scale at 5.3 kilograms or 12.2 minas. Following the formula we find the cube root of the product of 100 and 12.2 minas plus one tenth of the product equals 11.9 dactyls. 11.9 dactyls are equal to 230 mm. This leads to the conclusion that ‘caliber’ for the Greeks was a circumferential measurement. If we presume that the missile is either round or spherical, then 230 mm must its circumference.
By a simple algebraic manipulation of the formula for the circumference of a circle we can calculate the diameter, or modern day caliber, of the projectile at 70 mm! The barrel length is found by multiplying the caliber of the bore, 70 mm, by 17. The product is 1190 mm or a tube length of 62 dactyls. This presentation can only lead us to stand in awe of the cerebral capacity of the ancient Greeks. The precision of thought of these masters of rationality, the taproot of the western intellectual heritage, leaps across three millennia.
This foresight, if you pardon a shooting pun, on the part of the early Greeks comes as no surprise when you consider that the mathematician Eratosthenes used geometry to measure the circumference of the earth to an accuracy of a few percent some 3,000 years ago. Yes, indeed, the Greeks had a word for it.
