In guns, particularly firearms, but not artillery, where a different definition may apply, caliber is the specified nominal internal diameter of the gun barrel bore – regardless of how or where the bore is measured and whether the finished bore matches that specification. It is measured in inches or in millimeters. In the United States it is expressed in hundredths of an inch; in the United Kingdom in thousandths; and elsewhere in millimeters. For example, a US "45 caliber" firearm has a barrel diameter of roughly 0.45 inches (11.43mm). Barrel diameters can also be expressed using metric dimensions. For example, a "9 mm pistol" has a barrel diameter of about 9 millimeters. Since metric and US customary units do not convert evenly at this scale, metric conversions of caliber measured in decimal inches are typically approximations of the precise specifications in non-metric units, and vice versa.
The formal definition of large-calibre artillery used by the United Nations Register of Conventional Arms (UNROCA) is "guns, howitzers, artillery pieces, combining the characteristics of a gun, howitzer, mortar, or rocket, capable of engaging surface targets by delivering primarily indirect fire, with a calibre of 76.2 mm (3.00 in) and above". This definition, shared by the Arms Trade Treaty and the Treaty on Conventional Armed Forces in Europe, is updated from an earlier definition in United Nations General Assembly Resolution 46/36L, which set a threshold of 100 mm (3.9 in). Several grammatical changes were made to that latter in 1992 and the threshold was lowered in 2003 to yield the current definition, as endorsed by UN General Assembly Resolution 58/54.
The 3.7 cm Flak 18/36/37 was a series of anti-aircraft guns produced by Nazi Germany that saw widespread service in the Second World War. The cannon was fully automatic and effective against aircraft flying at altitudes up to 4,200 m. The cannon was produced in both towed and self-propelled versions. Having a flexible doctrine, the Germans used their anti-aircraft pieces in ground support roles as well; 37 mm caliber guns were no exception to that. With Germany's defeat, production ceased and, overall, 37 mm caliber anti-aircraft cannon fell into gradual disuse, being replaced by the Bofors 40 mm gun and later, by 35-mm anti-aircraft pieces produced in Switzerland.
The bombard is a type of cannon or mortar which was used throughout the Late Middle Ages and the early modern period. Bombards were mainly large calibre, muzzle-loading artillery pieces used during sieges to shoot round stone projectiles at the walls of enemy fortifications, enabling troops to break in. Most bombards were made of iron and used gunpowder to launch the projectiles. There are many examples of bombards, including Mons Meg, the Dardanelles Gun, and the handheld bombard.
The Dardanelles Gun or Great Bronze Gun is a 15th-century siege cannon, specifically a super-sized bombard, which saw action in the 1807 Dardanelles operation. It was built in 1464 by Ottoman military engineer Munir Ali and modelled after the Basilic, the bombard crafted by Orban that was used for the Ottoman siege of Constantinople in 1453.
A dynamite gun is any of a class of artillery pieces that use compressed air to propel an explosive projectile. Dynamite guns were in use for a brief period from the 1880s to the beginning of the twentieth century.
The Dulle Griet is a medieval large-calibre gun founded in Gent (Ghent).
The 16 inch gun M1919 (406 mm) was a large coastal artillery piece installed to defend the United States' major seaports between 1920 and 1946. It was operated by the United States Army Coast Artillery Corps. Only a small number were produced and only seven were mounted; in 1922 and 1940 the US Navy surplussed a number of their own 16-inch/50 guns, which were mated to modified M1919 carriages and filled the need for additional weapons.
Orban, also known as Urban, was an iron founder and engineer from Brassó, Transylvania, in the Kingdom of Hungary, who cast large-calibre artillery for the siege of Constantinople by the Ottomans in 1453.
The 14-inch/45-caliber gun,, whose variations were known initially as the Mark 1, 2, 3, and 5, and, when upgraded in the 1930s, were redesignated as the Mark 8, 9, 10, and 12. They were the first 14-inch (356 mm) guns to be employed by the United States Navy. The 14-inch/45-caliber guns were installed as the primary armament aboard all of the United States Navy's New York-class, Nevada-class, and Pennsylvania-class battleships. The gun also saw service in the British Royal Navy, where it was designated BL 14-inch gun Mk II.
The Pumhart von Steyr is a medieval large-calibre cannon from Styria, Austria, and the largest known wrought-iron bombard by caliber. It weighs around 8 t and has a length of more than 2.59 m. It was produced in the early 15th century and could fire, according to modern calculations, an 800 mm (31 in) stone ball weighing 690 kg (1,520 lb) to a distance of roughly 600 m (2,000 ft) after being loaded with 15 kg (33 lb) of gunpowder and set at an elevation of 10°.
The 8"/55 caliber gun formed the main battery of United States Navy heavy cruisers and two early aircraft carriers. United States naval gun terminology indicates the gun barrel had an internal diameter of 8 inches (203 mm), and the barrel was 55 calibers long.
In artillery, caliber or calibre is the internal diameter of a gun barrel, or, by extension, a relative measure of the barrel length.
The 8-inch Navy gun Mk.VI M3A2 on railway mount M1A1 was a World War II improved replacement for the World War I-era 8-inch M1888 gun and was used by the US Army's Coast Artillery Corps in US harbor defenses. The guns were also mounted in fixed emplacements on the barbette carriage M1A1. These guns were US Navy surplus 8"/45 caliber guns from battleships scrapped under the 1922 Washington Naval Treaty. Mark VI was the Navy designation. The Army designation for this gun was "8-inch Navy gun Mk.VI M3A2".
The Type 41 3-inch (76 mm) naval gun otherwise known as the 8 cm/40 3rd Year Type naval gun was a Japanese dual-purpose gun introduced before World War I. Although designated as 8 cm (3.15 in), its shells were 76.2 mm (3 in) in diameter.
The 8"/45 caliber Mark 6 gun were used for the secondary batteries of the United States Navy's last pre-dreadnought battleships and refitted in older armored cruisers main batteries.
The 7"/44 caliber gun Mark 1 and 7"/45 caliber gun Mark 2 were used for the secondary batteries of the United States Navy's last generation of pre-dreadnought battleships, the Connecticut-class and Mississippi-class. The 7-inch (178 mm) caliber was considered, at the time, to be the largest caliber weapon suitable as a rapid-fire secondary gun because its shells were the heaviest that one man could handle alone.
The 13"/35 caliber gun Mark 1 was used for the primary batteries on eight of the first nine battleships in the United States Navy, Indiana-class, Kearsarge-class and Illinois-class; USS Iowa (BB-4) used the 12-inch (305 mm)/35 caliber gun.
The 4″/40 caliber gun was used for the secondary batteries on the United States Navy's battleship Iowa, Columbia-class protected cruisers, and the armored cruiser New York, and was the primary batteries on the gunboats Nashville, Wilmington, and Helena.
The 6"/50 caliber gun Mark 6 and Mark 8 were used for the secondary batteries of the United States Navy's Maine-class and Virginia-class battleships, as well as the Pennsylvania-class and Tennessee-class armored cruisers. They were also used as the main battery on the St. Louis-class protected cruisers.
