Today, I want to talk about a tedious, but recurring, subject that has been the source of much confusion and ire. So, rather than addressing it in every other video, we're going to take a brief dive into the incredibly pedantic subject of how barrel, projectile, and cartridge sizes are named. So, let's go all the way to the beginning and wade into the chaos. And remember: if you think I'm wrong, fight me in the comments; if you can prove I'm wrong, please go publish. We could use the source reference. 

Uncovering the origins of Western firearms nomenclature is a daunting task, principally because nearly all of the earliest surviving literature on the subject in the English language comes from the late 1500s, a full two centuries after their arrival in Europe. By that time some of our most commonly associated words had already begun to take on something close to their current meanings and their true origins had been lost to the fog of medieval warfare. Attempting to trace the etymology of these words will take you into the abyss of ancient history, and is beyond the scope of this video.

Early black powder technology traveled out of Asia, through the Middle East, and by the 1300s into a region of the world that had once been ruled by the Roman Empire. Throughout this region, spanning from North Africa to Hadrian's Wall in England, the most common measurement used in commercial trade came from a Latin term "libra pondo", which means standard measure by weight. It was a system where goods were measured against a standard weight set for the goods being traded. While this varied based on the type of goods and the local ruler or organization which set the standard, it was a system everyone understood. As the Roman Empire fractured and faded, the system remained. The term evolved among the Romance Languages with variations of libra, and among Germanic and Celtic languages as variations of pondo. Which is where we get the English word pound. 

Identifying early guns eventually settled into a rough naming-convention that was loosely based on their overall weight. This was effective enough because a larger, heavier, gun was required to fire a larger, heavier, projectile. Quickly though, bronze was replaced by brass and iron and the categories became increasingly broad. Because each metal has a significantly different density and pressure capacity, total weight could vary immensely despite having roughly the same bore size. 

The term bore comes from an Old English word which describes both a tool and the opening which the tool makes. It wasn't until the late 1500s that metallurgy and manufacturing technology allowed barrels to be created by boring, but coincidentally, the earliest surviving English texts describing the inner recess of a gun barrel also date to this time and use the term. Although earlier terms exist in other languages, the English translation so far as we know has always been bore. Naming for the size of the bore, however, is quite a bit more complicated due to the fact that it is inextricably linked to the size of the projectile fired.

During the entire black powder era the diameter of a barrel bore was slightly larger than the projectile. This difference in size was called windage. The earliest projectiles used were bolts similar to those of the crossbow, but this quickly gave way to round balls, most typically cast of iron. With this, windage was especially important as it was necessary to prevent a ball from getting stuck in a barrel due to irregularities or excessive powder fouling, which could quickly turn a gun into an explosive. This is also where the word bullet comes from, being French for little ball. For the most efficient use of powder however, this gap needed to be sealed. In larger guns a fiber wad was used between the powder and the projectile and a patch of soft material, typically cotton or linen cloth, was also wrapped around the projectile to hold it in place before firing. With smaller firearms, the cloth patch typically accomplished both tasks and grease was often used to lubricate the patch and increase its effectiveness as a gas seal. It wasn't until the mid 1400s that it became common to use lead balls in smaller guns. Lead allowed for a much smaller windage gap and greatly decreased the chance of the ball becoming stuck in a barrel. Lead also increased the effectiveness of bullets due to it's greater weight, as a single charge of black powder can only push a projectile to a maximum velocity of approximately 2200fps, though guns small enough to be carried by a single man typically require significantly lower pressure and rarely exceed 1300fps.

Efforts to standardize bore size didn't really take place until the British began in the early 1500s. These efforts continued into the 1700s and eventually accomplished a system where gun sizes were standardized based on the projectile weight. While this system was primarily focused on the iron balls used in larger guns, it also applied to the lead balls used in smaller guns. Our subject is those smaller arms which used a round lead projectile weighing less than one pound.  In this system, the fraction of a pound was simplified as the numbered bore size. So a barrel firing a round lead projectile weighing one-quarter of a pound would be described as a 4 Bore. Likewise, a 50 Bore barrel fired a round lead ball weighting one-fiftieth of a pound.  

At the same time, on the rest of the European continent, another term referring to the weight of a projectile had taken hold stemming from a Latin term; caliber. It wasn't until the introduction of the Metric system after 1795, that caliber began to be expressed in units of length rather than weight. English use of the word mirrored this change and the British slowly began describing guns in both pounds and inches.

While they did not adopt the Metric system at this time, the need for a similarly global standard became increasingly important. This was done with the 1824 Weights and Measures Act, which standardized one pound as equal to 7000 grains. Prior to this the pound was not standardized across individual regions of England, let alone the rest of Europe. An 1855 revision of the Act further standardized bore size with the introduction of a royal gauge by which it was measured. This somewhat arbitrary implementation is why the numbered bore sizes are listed as a gauge in the Measures Act and why the gauge system does not exactly match the numbered bore system. Thank you, King George IV.

It was also around this time that barrel rifling became common, despite it's invention over 300 years earlier. Rifling is created by cutting grooves further into the bore of the barrel. This nomenclature in self evident. Why the remaining bore surface is then called a land, does not seem to have a surviving explanation. As rifling became more prevalent and the British drifted toward the Metric system, the numbered bore size faded into obscurity, being replaced by length-based caliber. The gauge system, however, continued to be used describing smooth-bore guns, particularly those which fired multiple round balls significantly smaller that the size of the bore, and came to be know as shotguns. 

In early rifles the same cloth patch that was used to take up the windage gap was also effective to engage the rifling. More effective, however, was using a lead ball slightly larger than the bore, which directly engaged the rifling. This, though, moved the windage problem from the bore to the grooves. To solve this problem a wad was used along with mixture of wax and grease. Between 1830 and 1850 a new style of projectile emerged. It was a conical bullet with a hollow base. This allowed the bullet to still easily fit down the bore of the barrel but when fired the base would expand to engage the rifling. This provided greater accuracy and allowed a range of bullet weights to be used in a single rifle. It also moved the grease from between the wad and bullet, to grooves made on the bullet itself.

And this is were naming conventions start getting rather arbitrary. Up to this point the bore size was relatively straightforward, windage and rifling aside, the projectile was essentially the same size as the bore and that size was used to name both. The biggest change came with the increasingly common use of multi-shot small arms which had a chamber separate from the barrel, such as a revolver. Because the bullet no longer had to pass through the barrel before firing it could be made solid at a diameter large enough to engage the rifling. Ironically, this allowed the round ball to be used much longer than it otherwise may have been. In these types of arms, the wax and grease mixture was typically applied over the bullets to also prevent hot gasses from igniting powder in the other chambers. 

On barrels themselves the term bore was increasingly being used to describe both the smaller inner diameter and the larger groove diameter. Additionally, the size of the projectile was now somewhere between these two dimensions. As packet-loading evolved into paper cartridges, a new type of industry producing ammunition also evolved, and manufacturers began naming cartridges, and the guns that fired them, after the size of the bullet. A new type was also developed for paper cartridges, called a heeled-bullet, which was solid with a recessed base and a grease groove toward the nose. This heel allowed the paper or linen casing to be attached to the bullet without tearing when the whole thing was shoved into a chamber. As cartridges transitioned to metal cases and breach-loading became standard, heeled-bullets continued to be used and the case and bullet had the same outer diameter. 

The widespread use of cartridges also coincided with greater regulations on commercial trade, and use of the patent system. At the same time, industrialization had brought about the modern era of brand identity. Firearm and ammunition manufactures began building brands around the reputation of their cartridges.

And this is when naming conventions began their descent into near anarchy. In Europe the old system continued, naming cartridges after the inner bore diameter, most consistently with rifle cartridges, although some were named after the bullet diameter. With pistol cartridges they were less consistent and often used either the groove or bullet diameter. In the United States, cartridges were typically named based on the nominal size of the bullet, commonly rounded up slightly to sound more appealing, with the exact bullet size varying between manufacturers. Manufacturers that produced multiple cartridges with the same bullet diameter also began including the case length in the cartridge name. This was short-lived in the U.S., but became standard with metric cartridges. To add to the chaos, cartridges which had a tapered or bottle-neck design saw the introduction a hyphenated name. In England, with cartridges like the 577-450, the name designated the original cartridge, and the smallest bore diameter of the rifle. In the United States, the Spencer company introduced a line of tapered cartridges where the name denoted the outer case diameter at the base and the neck.

The next significant development in bullet technology was the use of inside-lubricated bullets. The heel was no longer necessary and the lube groove was simply moved toward the base, with cartridge cases being made longer to cover them. This had little effect on rifle cartridges, as the chamber and case were simply made larger to accommodate the new style of bullet. In revolvers, however, manufacturers, Colt in particular, avoided the cost of installing new production lines to change the dimensions of their barrels and cylinders by simply using smaller diameter bullets. With bullets being once again roughly the same size as the inner bore diameter of the barrel, the old solution of using a hollow-base returned. Having put so much cost and effort in building the brand of the old style cartridges, however, the names were maintained despite the significant decrease in bullet size. 

Here, another, slightly more standardized, hyphenated naming convention was introduced in the United States. This new system designated the nominal size of the bullet in inches, the charge of black powder in grains, and the weight of the bullet in grains. This system was applied to both rifle and pistol cartridges. Eventually the weight of the bullet was dropped from the name, due to the wide availability of bullet weights in the same cartridge case.

Brand identity and increasing precision in manufacturing continued to add fuel to the chaos. Within the United States, the most common .45 caliber rifle cartridge was the 45-70, developed by the U.S. Ordnance Department, which used a .458" bullet. In .45 caliber pistols, however, the standard was set on Colt's cartridge, which used a .452" bullet. Meanwhile in England, the standard size of 45 caliber rifle and pistol bullets was .455". Continental Europe continued to typically name cartridges after the smallest bore diameter, expressed in millimeters to two decimals. However, because decimal millimeters are considerably larger than decimal inches, this led to inconsistent labels when producing cartridges developed in Imperial Units. Similarly, on the rare occasion metric cartridges were introduced into England or the United States, the metric designation might be kept, or it might be given an caliber name in inches based on the bullet diameter. 

The introduction of smokeless powder did nothing to alleviate this confusion, as the hyphenated naming system continued to be used into the 1890s, despite there being no designation in the name to indicate whether the cartridge was designed for black or smokeless powder.

The Turn of the Twentieth-Century saw yet another hyphenated naming convention introduced by the U.S. Ordnance Department. During efforts to update their service cartridge to compete with the 7x57mm Mauser, a cartridge was developed officially called the Caliber .30 Ball Model of 1901. This unwieldy official designation was shortened to simply 30-01, designating the nominal caliber and the model year. This naming convention was short lived within the military, only being applied to the 30-03 and 30-06. However, when later cartridges used the 30-06 as a parent case a hyphenated name was typically given with the nominal caliber and the 06 designation. 

Keep in mind though that throughout the 1800s, as each new naming convention was introduced, all the previous ones were generally still in use. As more and more cartridges were released during the early 1900s, European and American organizations were created to standardize and publish specifications for the widely varying and arbitrarily named cartridges. In the 21st Century the chaos continues as manufacturers release cartridges with whatever name is thought to sound the most modern or attractive, and may or may not accurately describe the bore size or bullet diameter. 

In conclusion, the tumultuous journey and incredible speed of advancing manufacturing technology and evolving trade regulation between 1800 and 1900 is how we arrived in our current era, with cartridge names, barrel dimensions, and caliber designations seemingly pulled from chaos.  

A simple "rule-of-thumb" is that bore size most accurately describes the smallest inner diameter of the barrel, but is commonly used to refer to both the land and groove diameters. Caliber, although widely misused to simply mean the cartridge name, is actually a measure of length. It may refer to the land or groove diameter of the barrel, or to the diameter of the bullet, depending on what naming convention you choose to use. Gauge is currently only used when referring to shotguns and has its own set of standards that were established in 1855, but can roughly be estimated by using the numbered bore system. A numbered bore size refers to weight, representing the fraction of a pound for a round ball with the same diameter as the bore.