Caliber (artillery)

In artillery, caliber or calibre[nb 1] is the internal diameter of a gun barrel, or by extension a relative measure of the length.

Calibre bore length gdl
Relationship of caliber in bore and length of gun.

Rifled barrels

Rifled barrels introduce ambiguity to measurement of caliber. A rifled bore consists of alternating grooves and lands. The distance across the bore from groove to groove is greater than the distance from land to land. Projectiles fired from rifled barrels must be of the full groove to groove diameter to be effectively rotated by the rifling, but the caliber has sometimes been specified as the land to land diameter before rifling grooves were cut. The depth of rifling grooves (and the consequent ambiguity) increases in larger calibers. Steel artillery projectiles may have a forward bourrelet section machined to a diameter slightly smaller than the original land to land dimension of the barrel and a copper driving band somewhat larger than the groove to groove diameter to effectively seal the bore as it becomes enlarged by erosion during prolonged firing. United States Navy guns typically used rifling depth between one-half and one percent of caliber. Projectile bourrelet diameter specification was 0.015 inches (0.38 mm) less than land to land diameter with a minus manufacturing tolerance so average clearance was about 0.012 inches (0.30 mm). Driving band diameter was groove to groove diameter plus 0.02 inches (0.51 mm).[1]

Barrel length

The length of the barrel (especially for larger guns) is often quoted in calibers. For example, US Naval Rifles 3 in (76 mm) or larger.[2] The effective length of the barrel (from breech to muzzle) is divided by the barrel diameter to give a dimensionless quantity.[2]:81 As an example, the main guns of the Iowa-class battleships can be referred to as 16"/50 caliber. They are 16 inches in diameter and the barrel is 800 inches long (16 × 50 = 800). This is also sometimes indicated using the prefix /L; so for example, the most common gun for the Panzer V tank is described as a "75 mm /L70," meaning a barrel with an internal bore of 75 mm, and 5,250 mm long (17 ft 2.69 in).

The bore to barrel length ratio is called caliber in naval gunnery,[2]:81 but is called length in army artillery. Before World War II, the US Navy used 5"/51 caliber (5"/L51) as surface-to-surface guns and 5"/25 caliber (5"/L25) as surface to air guns. By the end of World War II, the dual purpose 5"/38 caliber (5"/L38) was standard naval armament against surface and air targets. All three had a bore diameter of 5 inches (not 5.51 or 5.25 or 5.38 as often misread).

Naval rifles, although constructed and manufactured in roughly the same manners as land based artillery, were built to much more stringent and studious standards than land based weapons, and for good reason. At sea, a weapon had to perform, without fail. There was no ready replacement, nor one that could be readily supplied. Over time, the terms of pound (weight of shell) and bore (the actual bore of the weapon) became confused and blurred. Eventually, when the technology existed, the bore (in inches or millimetres) came to be the standard measure. For naval rifles, the initial change was to actual bore, thus facilitating the manufacture of standard projectiles. They then began to measure the effective length (and therefore range) of the weapon in calibers. These were (and are) a measure of the standardized bore of the barrel versus the rifled bore of the barrel. In other words, a 12/45 is 12"×45= the length of the rifled bore of that gun in inches. This explains the differences in both penetration and long range performance of various naval rifles over the years. In addition to the possible improvements in overall performance (i.e. muzzle velocity and striking force), the increase in barrel length also allowed, in some circumstances, an increase in projectile size as well. For example, the American 14/45, as introduced in the New York-class battleships, fired a 1250 lb. projectile. Later improvements to the design, lengthening the rifle itself and also altering the breech, allowed a 1400 lb. projectile and, overall, a greater barrel life. Again we see this pattern with the US 16" guns. The initial design was 45 calibers in length and fired a 2200 lb. shell. The later re-design to 50 calibre not only allowed a higher velocity but also a heavier 2700 lb. shell, which ultimately came to be accepted as the greatest naval shell ever deployed in combat.[3][4][5][6]

Early gun barrels were short and thick, typically no more than 26 calibers, as the gunpowder propellant they used burned very quickly and violently, and hence its acceleration time was short. Slower-burning "brown powder" formulations of gunpowder allowed gun barrel length to increase slightly in the 1880s but enormous quantities of brown powder were required. New slower-burning "smokeless powder" propellants available from the 1880s onwards such as Poudre B, cordite and nitrocellulose allowed a gentler prolonged acceleration, hence gun barrels were made progressively longer and thinner. The new formulations were far more powerful propellants than gunpowder and far less was needed by weight as they transformed almost entirely to gasses when burned. Muzzle velocity became limited only by the length of barrel that was feasible, both in terms of the construction methods of the day and in terms of any practical constraints imposed by the gun's manner of use.

The practical effect of long barrels for modern guns is that the projectile spends more time in the barrel before it exits, and hence more time is available for expanding gas from the controlled burning of the propellant charge to smoothly accelerate the projectile, bringing about a higher velocity without placing undue strain on the gun. In internal ballistics terms, if the base of a projectile is thought of as a piston propelled by the expanding gas, then as barrel length increases the volume swept by the piston also increases, and hence the amount of energy that can be extracted from the gas's burning increases. A longer barrel allows more propellant to be used: the propellant is all burned fairly early in the projectile's journey along the barrel, except in the very common instance where combustion is still occurring as the projectile leaves the muzzle and a visible muzzle "flash" is produced.

The projectile continues to accelerate as long as the pressure behind it is sufficient to overcome bore friction. The excess energy will continue to accelerate the projectile until it exits the muzzle. If the pressure behind the projectile drops sufficiently before the projectile leaves the bore, the projectile can and will slow while still within the barrel, despite residual bore pressure behind the projectile. A light charge with insufficient pressure to expel the projectile will result in a "squib", or projectile lodged in the bore. [7] This pressure is reduced by the increasing barrel volume the gas has to fill, and in order to achieve maximum muzzle velocity with the shortest barrel length, the projectile should exit the barrel as the gas pressure reduces to a small fraction of the maximum, although unlike chamber maximum chamber pressure, the small fraction desired is impossible to measure. In modern guns, increased muzzle velocities can be produced by altering powder composition and/or using duplex charges containing two different powders in order to extend the "pressure curve" further down the bore. By exposing the projectile base to a given pressure for a longer length of time, velocity can be increased without elevating the pressure level generated.

Technological improvements had made it possible to introduce into use long gun barrels that are strong enough to withstand the forces involved in accelerating the shell to a high velocity, while remaining light enough to be reasonably mobile, rigid enough to maintain accuracy, and having a bore able to withstand many firings before needing refurbishment. In World War I 45-caliber naval gun barrels were typical, in World War II 50- to 55-caliber barrels were common, with Germany already manufacturing tank guns of 70 calibers by 1943.

Today 60- to 70-caliber barrels are not uncommon, but the latest technology has allowed shorter barrels of 55 calibers to attain muzzle velocities of 1,750 m/s (5,700 ft/s), as with the Rheinmetall 120 mm tank gun. However, by using discarding sabots, many such guns fire projectiles which are much smaller than the gun bore; so the relationship of projectile size to barrel length is not as straightforward as with older ordnance.


  1. ^ difference in British English and American English spelling
  1. ^ Fairfield, A.P. (1921). Naval Ordnance. Annapolis, Maryland: United States Naval Institute. pp. 501–508.
  2. ^ a b c Naval Ordnance And Gunnery, Volume 1, Naval Ordnance, NAVPERS 10797-A (1957 ed.). Washington, D.C.: U.S. Navy, Bureau of Naval Personnel. 1957. p. 81.
  3. ^ Rowland, B et al.
  4. ^ Gun Mount and Turret Catalog (OP 1112, 1945 ed).
  5. ^ FTP-45 (General Fleet Tactics 1924).
  6. ^ FTP-188 (General Fleet Tactics 1940).
  7. ^ Canadian Army. B-GL-306-006/FP-001, 1992-06-01
2S7 Pion

The 2S7 Pion ("peony") or Malka is a Soviet self-propelled cannon. "2S7" is its GRAU designation.

It was identified for the first time in 1975 in the Soviet Army and so was called M-1975 by NATO (the 2S4 Tyulpan also received the M-1975 designation), whereas its official designation is SO-203 (2S7). Its design is based on a T-80 chassis carrying an externally mounted 2A44 203 mm gun on the hull rear.


The AK-176 is a Soviet naval gun mounted in an enclosed turret, that may be used against sea, coastal, and aerial targets, including low flying anti-ship missiles. The system is designed to arm small displacement ships and comprises the Gun Mount with a MR-123-02/76 Fire Control Radar System. It has high survivability owing to autonomous use of the gun mount controlled from the optical sight in the absence of control from the radar system, as well as a capability for fire, if power supply is lost.

Attack aircraft

An attack aircraft, strike aircraft, or attack bomber, is a tactical military aircraft that has a primary role of carrying out airstrikes with greater precision than bombers, and is prepared to encounter strong low-level air defenses while pressing the attack. This class of aircraft is designed mostly for close air support and naval air-to-surface missions, overlapping the tactical bomber mission. Designs dedicated to non-naval roles are often known as ground-attack aircraft.Fighter aircraft often carry out the attack role, although they would not be considered attack aircraft per se, although fighter-bomber conversions of those same aircraft would be considered part of the class. Strike fighters, which have effectively replaced the fighter-bomber and light bomber concepts, also differ little from the broad concept of an attack aircraft.

The dedicated attack aircraft as a separate class existed primarily during and after World War II. The precise implementation varied from country to country, and was handled by a wide variety of designs. In the United States and Britain attack aircraft were generally light bombers or medium bombers, sometimes carrying heavier forward-firing weapons like the North American B-25G Mitchell and de Havilland Mosquito Tsetse. In Germany and the USSR, where they were known as Schlachtflugzeug ("battle aircraft") or sturmovik ("storm trooper") respectively, this role was carried out by purpose-designed and heavily armored aircraft such as the Henschel Hs 129 and Ilyushin Il-2. The Germans and Soviets also used light bombers in this role: cannon-armed versions of the Junkers Ju 87 Stuka greatly outnumbered the Hs 129, while the Petlyakov Pe-2 was used for this role in spite of not being specifically designed for it.

In the latter part of World War II the fighter-bomber began to take over many attack roles, a transition that continued in the post-war era. Jet-powered examples were relatively rare but not unknown, such as the Blackburn Buccaneer. The U.S. Navy continued to introduce new aircraft in their A-series, but these were mostly similar to light and medium bombers. The need for a separate attack aircraft category was greatly diminished by the introduction of precision-guided munitions which allowed almost any aircraft to carry out this role while remaining safe at high altitude. Attack helicopters also have overtaken many remaining roles that could only be carried out at lower altitudes.

Since the 1960s, only two dedicated attack aircraft designs have been widely introduced, the American Fairchild Republic A-10 Thunderbolt II and Soviet/Russian Sukhoi Su-25 Frogfoot. One anomaly belonging to this class is the Lockheed AC-130, which features as its primary armament high-caliber artillery guns adapted for aircraft use including the 105 mm M102 howitzer.

A variety of light attack aircraft have also been introduced in the post-World War II era, usually based on adapted trainers or other light fixed-wing aircraft. These have been used in counter-insurgency operations.

Battle of Lushunkou

The Battle of Lüshunkou (Chinese: 旅順口之戰; Japanese: Ryōjunkō-no-tatakai (旅順口の戦い)) was a land battle of the First Sino-Japanese War. It took place on 21 November 1894 in Lüshunkou, Manchuria (later called Port Arthur, in present-day Liaoning Province, China) between the forces of the Empire of Japan and the Empire of China. It is sometimes referred to archaically in western sources as the Battle of Port Arthur (that name is now primarily used for the opening battle of the Russo-Japanese War in 1904).

GCT 155mm

The GCT 155 mm is a French self-propelled gun vehicle currently in use by the armies of France and Saudi Arabia. It replaced the former Mk F3 155mm in French Army service. The GCT 155mm's primary advancement is that it incorporates and provides full armor and nuclear-biological-chemical (NBC) protection for its crew of four, while the former Mk F3 155mm offered no protection and could carry only two of its four crew members. Though 60% heavier than the American M109, the GCT 155mm is faster, fires faster and incorporated a more sophisticated fire control system. The GCT 155mm saw combat with the Iraqi Army in the Iran–Iraq War.

Gardner gun

The Gardner gun was an early type of mechanical machine gun. It had one, two or five barrels, was fed from a vertical magazine or hopper and was operated by a crank. When the crank was turned, a feed arm positioned a cartridge in the breech, the bolt closed and the weapon fired. Turning the crank further opened the breechblock and extracted the spent case.

Ouvrage Les Sarts

Ouvrage Les Sarts is a petit ouvrage of the Maginot Line, built as part of the "New Fronts" program to address shortcomings in the Line's coverage of the border with Belgium. Like the other three ouvrages near Maubeuge, it is built on an old Séré de Rivières system fortification, near the town of Marieux.


Rail-gun, railgun or rail gun may refer to:

Railway gun, a large caliber artillery piece mounted on a railcar for rail mobility

Railgun, an entirely electrical gun which uses a homopolar motor to accelerate projectiles

Coilgun, an entirely magnetic gun which uses a linear motor to accelerate projectiles

Helical railgun, combines the railgun and the coilgun

Benchrest rifle, also known as a rail gun, a type of rifle that is built into a machine rest

A Certain Scientific Railgun, a spin-off manga and anime series

Mikoto Misaka, also known as "Railgun", protagonist of the spin-off series and a character from A Certain Magical Index series of light novels and anime.

Russian cruiser Admiral Nakhimov (1885)

Admiral Nakhimov (Russian: Адмирал Нахимов), was an armoured cruiser in the Imperial Russian Navy during the Russo-Japanese War. She was named after Admiral Pavel Nakhimov.

SMS Kronprinzessin Erzherzogin Stephanie

SMS Kronprinzessin Erzherzogin Stephanie was an ironclad warship built for the Austro-Hungarian Navy in the 1880s, the last vessel of that type to be built for Austria-Hungary. The ship, named for Archduchess Stephanie, Crown Princess of Austria, was laid down in November 1884, was launched in April 1887 and completed in July 1889. She was armed with a pair of 30.5-centimeter (12.0 in) guns in open barbettes and had a top speed of 17 knots (31 km/h; 20 mph). Her service was limited, in large part due to the rapid pace of naval development in the 1890s, which quickly rendered her obsolescent. As a result, her career was generally limited to routine training and the occasional visit to foreign countries. In 1897, she took part in an international naval demonstration to force a compromise over Greek and Ottoman claims to the island of Crete. Kronprinzessin Erzherzogin Stephanie was decommissioned in 1905, hulked in 1910, and converted into a barracks ship in 1914. After Austria-Hungary's defeat in World War I, the ship was transferred to Italy as a war prize and was eventually broken up for scrap in 1926.

Scioto Ordnance Plant

The Scioto Ordnance Plant (SOP) was an ammunitions and bomb making facility built in Marion County, Ohio by the United States Army in 1942. The plant operated until 1945 when production wound down. Also built adjacent was the Marion Engineering Depot which was authorized in the summer of 1942. Land for the plant was taken in Grand Prairie, Scott, Clairdon and Marion Townships in an area covering 12,500 acres (51 km2).

Families who owned property within the zone identified for the facility were notified March 2, 1942 that they had to vacate their land by May 1, 1942. Not only did this mean that the displaced had to find a place to live in the midst of a housing and fuel shortage, but it also meant moving and/or selling livestock and agricultural equipment. Federal contractors began removing field fencing in April 1942. While land owners received a "fair" valuation for their property, relocation expenses were not paid. Several property owners claimed that they never received any compensation from the government.

After May 1, 1942, most of the farmsteads located inside the perimeter were leveled; underground bunkers and production buildings were built in clusters throughout the SOP site. By June 1942 SOP was employing 2,900 employees, many of whom moved north from Southern Ohio and Kentucky for the high paying wages offered.

Once in operation, the plant (under the operation of U.S. Rubber) produced fuses and boosters, 20 mm bullets, 50 caliber bullets, 50 caliber artillery shells, 65 mm shells and 75 mm shells. Incendiary bombs and napalm barrel bombs, similar to those used on Dresden by Allied forces were also produced at the site. Munitions containers served duel duty by carrying SOP products overseas, and then doubling as coffins for those killed in action.

German Prisoners of War were housed on the site (in an area referred to as “Camp Marion”) beginning in December 1944.

Self-propelled gun

A self-propelled gun (SPG) is a form of self-propelled artillery, and in modern use is usually used to refer to artillery pieces such as howitzers.

Self-propelled guns are mounted on a motorized wheeled or tracked chassis (because of this they are sometimes visually similar to tanks). As such the gun can be maneuvered under its own power as opposed to a towed gun that relies upon a vehicle or other means to be moved on the battlefield. Self-propelled guns are combat support weapons; they are employed by combat support units fighting in support of, or attached to, the main combat units: infantry and armour (tanks). Self-propelled guns are best at providing indirect fire but can give direct fire when needed.

It may be armoured, in which case it is considered an armoured fighting vehicle (AFV). Typically, self-propelled guns are more lightly armoured and may not have turrets and their purpose is distinct from that of tanks.

The greatest tactical advantage in the case of artillery guns is clearly the greater degree of mobility they have compared to towed artillery. Not only is it important in offering military forces greater flexibility, but it is critical in avoiding attack from the enemy (counter-battery fire) by allowing the guns to change position immediately after firing one or more salvos and before their position can be located ("shoot-and-scoot" tactics). A secondary advantage in the case of – even lightly – armoured guns is the increased protection offered to the gun crews.

Toyokawa Naval Arsenal

The Toyokawa Naval Arsenal (豊川海軍工廠, Toyokawa kaigun kōshō) was a major production facility for aviation ordnance, light arms, and ammunitions for the Imperial Japanese Navy during World War II. It was located in what is now part of the city of Toyokawa, Aichi Prefecture, Japan. It was one of the largest armaments plant in the Empire of Japan, but was not bombed by Allied forces until after the bombing of Hiroshima in World War II.

Transparency in Armaments

Transparency in Armaments (TIA) is an arms control reporting program established by the United Nations General Assembly on December 9, 1991 under UN resolution 46/36L. It calls for annual reporting by UN member states on imports, exports, and holdings of weapons in seven categories: battle tanks; armored combat vehicles; large caliber artillery systems; attack helicopters; combat aircraft; warships; and missiles and missile launchers. Reporting is not required but is strongly encouraged. Reports are sent to the Secretary General of the United Nations and are maintained in the United Nations Conventional Arms Register (UNCAR).

Reporting has not been consistent. At least 170 member states and three non-member states have reported at least once since reporting began. However, in 2010, only 72 national reports were received. The highest rate of compliance is by nations that are members of the Organization for Security and Co-operation in Europe (OSCE), because the data required by TIA is comparable to that required by other OSCE arms control initiatives.

Type 14 10 cm cannon

The Type 14 10 cm cannon (十四式十糎加農砲, Jyūyon-shiki Kanōhō) was the first medium caliber cannon totally of Japanese design and the first with a split trail carriage. The Type 14 designation was given to this gun as it was accepted in the 14th year of Emperor Taishō's reign (1925). It was used Imperial Japanese Army but was not considered successful and was replaced by the Type 92 10 cm cannon.

USS Corry (DD-463)

USS Corry (DD-463), a Gleaves-class destroyer, (also known as the Bristol class), was the second ship of the United States Navy to be named for Lieutenant Commander William M. Corry, Jr., an officer in the Navy during World War I and a recipient of the Medal of Honor.

Corry was launched 28 July 1941 by Charleston Navy Yard, sponsored by Miss Jean Constance Corry. The ship was commissioned on 18 December 1941, Lieutenant Commander E. C. Burchett in command; and reported to the U.S. Atlantic Fleet.

Wassenaar Arrangement

The Wassenaar Arrangement on Export Controls for Conventional Arms and Dual-Use Goods and Technologies is a multilateral export control regime (MECR) with 42 participating states including many former Comecon (Warsaw Pact) countries.

The Wassenaar Arrangement was established to contribute to regional and international security and stability by promoting transparency and greater responsibility in transfers of conventional arms and dual-use goods and technologies, thus preventing destabilizing accumulations. Participating states seek, through their national policies, to ensure that transfers of these items do not contribute to the development or enhancement of military capabilities which undermine these goals, and are not diverted to support such capabilities.

It is the successor to the Cold War-era Coordinating Committee for Multilateral Export Controls (COCOM), and was established on 12 July 1996, in Wassenaar, the Netherlands, which is near The Hague. The Wassenaar Arrangement is considerably less strict than COCOM, focusing primarily on the transparency of national export control regimes and not granting veto power to individual members over organizational decisions. A Secretariat for administering the agreement is located in Vienna, Austria. Like COCOM, however, it is not a treaty, and therefore is not legally binding.

Every six months member countries exchange information on deliveries of conventional arms to non-Wassenaar members that fall under eight broad weapons categories: battle tanks, armoured fighting vehicles (AFVs), large-caliber artillery, military aircraft, military helicopters, warships, missiles or missile systems, and small arms and light weapons.

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