Shotguns: Different Gauges

Well, we did study shotgun bores/gauges in an earlier post. But it is hard to visualize the effects of the different gauges from just a description.

No fear, the lovely and talented Heather LaCroix is here, demonstrating the effects of 10 gauge vs. 12 gauge vs. 20 gauge vs. .410 caliber (67 gauge). Remember from our earlier discussion of how shotgun gauges work, the smaller the number, the bigger the diameter of the cartridge and the more powerful the gun.

Thanks to Heather LaCroix and Jeff3230 for the demonstration.

Bore & Gauge - II

In our last post, we studied how the bore/gauge of a firearm was specified. For larger weapons, such as cannons and field artillery, the diameter of the barrel would be specified in a related way.

In the case of a cannon, the diameter of the barrel is much more than that of a firearm. Hence, the bore would be specified in pounds (e.g.) 2 pounder, 3 pounder, 4 pounder, 6 pounder, 18 pounder, 24 pounder etc. This would often be appreviated as 2 pdr, 3 pdr, 4 pdr, 6 pdr etc. As with firearms, what this means is that if you took a solid spherical cannon ball that fit into (say) a 3 pounder barrel and weighed it, it would weigh 3 pounds. Similarly, a 6 pounder would use a cannon ball of such diameter that if you weighed it, it would weigh 6 pounds and so on. This establishes a relationship between the weight of the cannon ball and the bore diameter.

The difference between cannon bores and firearm bores is that in firearm bores, the material of the ball is considered to be lead, whereas with cannon bores, the cannon ball was considered to be made of iron. Since these materials have different densities, a 1 pound lead ball has smaller diameter than a 1 pound iron ball. Also, for firearm bores, when a firearm is said to be of N bore, that means the ball it takes weighs 1/N pounds. For instance, a 10 bore musket uses lead balls weighing 1/10 of a pound and a 12 bore musket uses balls weighing 1/12th of a pound. As a consequence of this, the smaller the bore number, the larger the diameter of the firearm's barrel (i.e. diameter of 2 bore > 4 bore > 10 bore etc.). In contrast to this, a cannon bore is specified by the weight of the iron cannon ball, so the larger number indicates a larger diameter barrel (16 pdr > 8 pdr > 3 pdr).

Even though two cannon might be both (say) 32 pounders, in practice though, the barrel diameters of cannon pieces varied between regions and countries, because there wasn't a world-standard for exactly how much a pound was. For example, during the time when Napoleon was leading the French around Europe, the French standard pound weighed around 489.5 grams (by modern SI standards), whereas the English standard pound weight was approximately 454 grams. Therefore, during this period, a French 32 pounder cannon would have a greater diameter than an English 32 pounder cannon, because the French 32 pounder cannon ball actually weighed about 1.14 kg more than an English 32 pound cannon ball!

This relationship between cannon ball weight and bore of the cannon began to become less connected once metallurgical techniques improved and it became practical and widespread to add rifling to cannon bores. By the 20th century, some forces, particularly British, still continued to class their weapons by the weight of the shot they fired. However, the projectile itself was no longer a solid spherical iron ball, but was more of a conical shaped hollow artillery shell with some explosive material inside. Hence, the weight of the shell had no real relationship with its diameter any more.

What is the Bore/Gauge of a Weapon?

In the medieval period, the inner diameter of a barrel was frequently referred to as the bore (or gauge) of the weapon, and different weapons were classified by their bore size. This designation still exists in the present day, when referring to shotguns (e.g. 8 bore, 10 bore, 12 gauge etc.) while most other weapons are classed in mm. or inches (for instance, 9 mm., .45 caliber etc.). So what is a bore/gauge and how is it measured.

To study that topic, we must go back to a time when bullets were cast round lead balls. The bore or gauge was determined from the weight of a solid ball of lead that could fit into the barrel. For instance, if a spherical ball weighing 1/10th of a pound could fit into the barrel, then the gun was considered to be 10 bore (or 10 gauge). If a ball weighing 1/12th of a pound could fit into the barrel, then it was 12 bore (or 12 gauge) and so on. Conversely, if you had 1 pound of lead available, you could cast 12 bullets for a 12 bore (or 12 gauge) gun and 10 bullets for a 10 bore (or 10 gauge) gun and so on. Even though bullets were no longer spherical shaped, this unit continued to be used into the 19th century to denote the barrel diameter, assuming that a spherical ball of lead was used.

As you might have gathered from the paragraph above, the smaller the bore number, the larger the diameter of the barrel. Therefore, a 4 bore gun would have a large diameter, since 1 pound of lead would only make 4 solid spherical bullets for this gun. As you might have guessed, 4 bore guns were called "Elephant Guns" and used to shoot large animals like elephants, buffaloes and rhinos.

In the picture above, we have 3 cartridges, left to right: a .30-06, an eight bore and a four bore cartridge. Note that the .30-06 is the cartridge used by the M1 Garand rifle and measures 7.62 x 63 mm. This gives the reader an idea of the size of one of these large bore bullets.

By the way, the four bore wasn't the largest elephant gun around. There was also the two bore. The two bore was only used by very few men because of its immense recoil and weight.

The above picture shows a .700 Nitro express bullet and cartridge case versus a 2 bore bullet and cartridge case. The diameter of a 2 bore is 33.68 mm and the bullet weighs over 225 grams! The famous British explorer, Sir Samuel White Baker, owned one such weapon and he was afraid to fire it. In his own words:

Among other weapons, I had an extraordinary rifle that carried a half-pound percussion shell; this instrument of torture to the hunter was not sufficiently heavy for the weight of the projectile: it only weighted twenty pounds, thus with a charge of ten drachms [270 grains] of powder and a HALF-POUND shell, the recoil was so terrific, that I spun around like a weathercock in a hurricane. I really dreaded my own rifle, although I have been accustomed to heavy charges of powder and severe recoils for some years. None of my men could fire it, and it was looked upon as a species of awe, and it was name "Jenna-El-Mootfah" (Child of a Cannon) by the Arabs, which being a far too long of a name for practice, I christened it the "Baby", and the scream of this "Baby" loaded with a half-pound shell was always fatal. It was too severe, and I seldom fired it, but it is a curious fact that I never shot a fire with that rifle without bagging. The entire practice, during several years, was confined to about twenty shots. I was afraid to use it, but now and then as it was absolutely necessary, it was cleaned after months of staying loaded. On such occasions my men had the gratification of firing it, and the explosion was always accompanied by two men falling on their backs (one having propped up the shooter) and the "Baby" flying some yards behind them. This rifle was made by Holland & Holland, of Bond Street, and I could highly recommend it for the Goliath of Gath, but not for the men of A.D. 1866.

The two bore was the largest rifle that could be fired from the shoulder. There are still larger calibers though. One of these examples is the 1 bore or punt gun, which was designed to be fired from a boat. We will discuss punt guns in a future post.